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For predators, cooperation can decrease the cost of hunting and potentially augment the benefits. It can also make prey accessible that a single predator could not catch. The degree of cooperation varies substantially and may range from common attraction to a productive food source to true cooperation involving communication and complementary action by the individuals involved. We here describe cooperative hunting of Galapagos sea lions (Zalophus wollebaeki) for Amberstripe scad (Decapterus muroadsi), a schooling, fast swimming semipelagic fish. A group of 6–10 sea lions, usually females only, drove scad over at least 600–800 m from open water into a cove where, in successful hunts, they drove them ashore. Frequently, these “core hunters” were joined toward the final stages of the hunt by another set of opportunistic sea lions from a local colony at that beach. The “core hunters” did not belong to that colony and apparently were together coming toward the area specifically for the scad hunt. Based on the observation of 40 such hunts from 2016 to 2020, it became evident that the females performed complementary actions in driving the scad toward the cove. No specialization of roles in the hunt was observed. All “core hunters” and also opportunistically joining sea lions from the cove shared the scad by randomly picking up a few of the 25–300 (mean 100) stranded fish as did scrounging brown pelicans. In one of these hunts, four individual sea lions were observed to consume 7–8 fish each in 25 s. We conclude that the core hunters must communicate about a goal that is not present to achieve joint hunting but presently cannot say how they do so. This is a surprising achievement for a species that usually hunts singly and in which joint hunting plays no known role in the evolution of its sociality., We describe cooperative hunting of groups of Galapagos sea lions (Zalophus wollebaeki) for Amberstripe scad (Decapterus muroadsi), a schooling, fast swimming fish which they drive ashore by complimentary actions. The “core hunters” were together coming to the area specifically for the scad hunt. We conclude that the core hunters must communicate about a goal that is not present to coordinate joint hunting which is a surprising achievement for a species that usually hunts singly and in which joint hunting plays no role in the evolution of its sociality.

Understanding behavioral ontogeny is important for the successful conservation of endangered marine mammals. This is particularly the case for phocid seals, as during the early stages of their life they must acquire, largely independently, essential survival skills. We studied the maternal behavior and early behavioral ontogeny of the Mediterranean monk seal, one of the most endangered marine mammals on Earth, by installing a remote-controlled, infrared, video system in a pupping cave in Greece and recording the behavior of 2 adult females and their newborn pups (September 2007 to March 2008). Behavioral observations focused on the monitoring of individual attendance (i.e. percentage of time spent in attendance and attendance time) and the description of interactions. Following parturition, the percentage of time spent in attendance of both mothers and pups decreased gradually as pups developed towards independence. Overall, the pupping cave was used almost continuously by the 4 individuals for 3 to 4 mo. Similarly, attendance times also decreased after parturition. During the first 10 d postpartum, maternal attendance was followed by a 0.5 to 13.8 h absence, during which we presume that the adult females went out foraging. We also detail various in-cave interactions for the first time in Mediterranean monk seals in Greece, including lactations, interactions between mothers and pups, interactions between pups and general seal interactions. Our study increases our understanding of the in-cave behavior of the Mediterranean monk seal, while highlighting the vital role of suitable caves in the reproduction and survival of the species and the necessity to effectively protect this type of habitat.

To survive and reproduce successfully, animals have to find the optimal time of breeding. Species living in nontropical environments often adjust their reproduction plastically according to seasonal changes of the environment. Information about the prevailing season can be transmitted in utero, leading to the adaptation of the offspring to the prevailing season. After birth, animals acquire additional personal information about the environment, which allows them to adjust their reproductive investment. Here, we tested in a full-factorial match–mismatch experiment the influence of reproductive adjustments according to maternal and personal information. We bred wild cavies (Cavia aperea), a precocial rodent, either into increasing (spring) or decreasing (autumn) photoperiod and, subsequently, after weaning, transferred female offspring to the matching or mismatching season. We measured growth, specific metabolic rate (sRMR) and reproductive events across six months. Although sRMR was elevated for females primed for good (spring) conditions when transferred to the mismatching autumn condition, we found no maternal effects on reproduction. Females adjusted their reproductive decisions according to the season they personally experienced, thereby implying a potentially high level of plasticity. Females reproducing in spring started reproduction earlier with a lower reproductive effort than females reproducing in autumn but, ultimately, the two groups did not differ in survival, growth, or reproduction. These data suggest important developmental plasticity, highlight the use of personal information acquired after weaning over early information provided until weaning, and point out the potential value of multiple cues, such as food abundance and quality and temperature besides photoperiod.

Understanding the ability of animals to cope with a changing environment is critical in a world affected by anthropogenic disturbance.1 Individual foraging strategies may influence the coping ability of entire populations, as these strategies can be adapted to contrasting conditions, allowing populations with foraging polymorphisms to be more resilient toward environmental change.2,3 However, environmentally dependent fitness consequences of individual foraging strategies and their effects on population dynamics have not been conclusively documented.4,5 Here, we use biologging data from endangered Galapagos sea lion females (Zalophus wollebaeki) to show that benthically foraging individuals dig after sand-dwelling prey species while pelagic foragers hunt in more open waters. These specialized foraging behaviors result in distinct and temporally stable patterns of vibrissae abrasion. Using vibrissae length as a visual marker for the benthic versus pelagic foraging strategies, we furthermore uncovered an environment-dependent fitness trade-off between benthic and pelagic foragers, suggesting that the foraging polymorphism could help to buffer the population against the negative effects of climate change. However, demographic projections suggest that this buffering effect is unlikely to be sufficient to reverse the ongoing population decline of the past four decades.6 Our study shows how crucial a deeper understanding of behavioral polymorphisms can be for predicting how populations cope within a rapidly changing world. VIDEO ABSTRACT. Copyright © 2022 Elsevier Inc. All rights reserved.

The Galapagos sea lion (GSL, Zalophus wollebaeki) is the smallest sea lion species in the world, endemic to the Galapagos archipelago and formerly considered a subspecies of the California sea lion (Zalophus californianus). Breeding rookeries occur throughout the archipelago. Females are highly site faithful; hence genetic exchange between rookeries occurs predominantly through male dispersal. Females start their reproductive career rather late at a mean age of 6 years, give birth to a single pup, and nurse it unusually long for between 2 and 4 years. If a female bears another pup during lactation, the newborn’s survival is seriously reduced. The extended period of maternal care lowers the reproductive rate to around 0.4 pups per adult female per year. Moreover, in years of strong El Nino events, pup mortality increases, and even older animals commonly die of starvation. Pups show distinct personalities such as shy and bold within their early social environment, thus shaping how they explore new situations and habitats. Once independent, diving strategies can also consistently differ between individuals: some forage via shallow dives, whereas others dive deep and/or mostly at night. Over the last 15 years, survival rates across all age classes have decreased in one important rookery located in the center of the species’ distribution. Recent demographic models in the Caamano rookery predict substantial population decrease in the coming years, likely to be further exacerbated by increasing sea surface temperatures due to global warming and more frequent El Nino events. Low abundance within a small distribution area makes the GSL vulnerable to a combination of anthropogenic and stochastic environmental disturbances. Fishery interactions, pressures from increased tourism, and habitat intrusion along with the potential for introduction of diseases are presently great dangers which may pose a serious threat to this endangered species.

The Galapagos fur seal (GFS; Arctocephalus galapagoensis) is the smallest seal species, endemic to the Galapagos archipelago and closely related to the South American fur seal, Arctocephalus australis. Females are highly site faithful. Genetic exchange between colonies happens predominantly through male dispersal. The species’ distribution overlaps with that of the Galapagos sea lion (Zalophus wollebaeki). The largest colonies exist on the western islands where cold, productive waters upwell. GFSs breed when upwelling is strongest, from August to December. They forage pelagically on organisms of the deep scattering layer, mostly cephalopods, myctophids, and bathylagids. These organisms migrate toward the surface when it gets dark, which brings them into the diving range of the GFS. Consequently, GFSs forage at night, and their foraging is strongly influenced by the lunar cycle. Females give birth to a single pup and nurse it usually for 2 years, but under poor environmental conditions may extend the time to weaning. If a female bears another pup during lactation, the newborn’s survival is seriously reduced. The extended period of maternal care lowers the reproductive rate. Moreover, in years of strong El Nino, offspring mortality is increased and even adult animals may die of starvation. The small distribution area and low population size make the GFS vulnerable to environmental disturbances, whether anthropogenic or natural like El Nino. Fishery interactions and the potential introduction of diseases are presently the greatest dangers. Tourism should be closely monitored and restricted to protect breeding sites.

Parent-offspring conflict over parental care is predicted to become most pronounced during offspring transition to independence when offspring are predicted to attempt to extend care for longer than parents are selected to provide it. However, on the proximate level, it is difficult to determine who plays the most important role in this process, parents or offspring. For several vertebrate taxa, it has been documented that parents end brood care by abandoning offspring after a fixed period or else show high flexibility in the duration of care, but teasing apart the role of offspring and parents underlying this flexibility has been difficult. Here, we studied the decision to fledge in captive zebra finches (Taeniopygia guttata), an altricial songbird. We experimentally delayed the time of fledging to determine who decides about the end of feeding inside the nest, parents or offspring. The experiment indicates that parents do not primarily rely on phenotypic offspring traits in their decision to feed offspring in the nest, but appear to adjust the duration of parental care as long as offspring are in the nest which parents may take as an indicator of offspring need and locomotor abilities. Delayed-fledging offspring appeared not to suffer a disadvantage in terms of age at the onset of independent feeding. Our study suggests that, in zebra finches, offspring play a major role in determining the time of fledging and leave the nest on their own, possibly to reduce the risk of nest predation, or to evade sibling competition in the nest.

Environmental variation strongly influences individual life histories, behavior, and immunity. For many animals living in non-tropical regions, environmental variation due to season is very important and can be reliably predicted by photoperiod. By manipulating the pre- and post-natal photoperiod for cavies (Cavia aperea), we simulated different birth seasons that go along with predictable differences in life history. Offspring born into simulated spring conditions mature earlier, indicating a fast pace of life compared to offspring born into simulated fall. We investigated the development of two innate (titers of natural antibodies and complement) and one adaptive (immunoglobulin G) immune effectors across multiple life stages. In addition, we tested if three behaviors, indicating risk-taking and stress-coping, differed between seasons. Finally, we tested if behaviors and immune traits correlate with each other as predicted by the pace-of-life syndrome hypothesis. The season of birth influenced average trait expression of both immunity and behavior. Boldness, indicating risk-taking behavior, correlated positively with the titers of natural antibodies, fitting the predictions of the pace-of-life syndrome (POLS). However, fearlessness, indicating how an individual copes with a stressful situation, correlated positively with immunoglobulin G concentrations, against the predictions of the POLS. Together, our results show that behaviors and immune traits react to differences in expected life histories, but do not show the predicted covariation. We conclude that proximate mechanisms and different functions of traits need to be considered to predict the nature of behavior-immune associations. Individual life histories, behavior, and immunity are strongly influenced by the environment individual's experience during early life. Recent theory predicts correlations between behavior and immunity to arise as a consequence of different life histories. By simulating different birth seasons, we induced different life history expectations as well as a season-dependent development of immunity and behavior. However, correlations between behavior and immunity do not fit theoretical predictions, highlighting the need for more detailed theory.

Summary The Guadalupe (Arctocephalus townsendi), Juan Fernandez (A. philippii), and Galapagos fur seals (A. galapagoensis) are three closely related species within the Family Otariidae. Their taxonomic status is currently an issue of debate; a new Genus Arctophoca has been suggested, but they are currently all classified as being Arctocephalus. Galapagos fur seal’s taxonomic position is also somewhat open as to whether it is an independent species or a subspecies of the South American fur seal (A. australis).

Summary We summarize the knowledge about the three species of Zalophus sea lions (one believed to be extinct: the Japanese sea lion), explain the latest state of the taxonomy, and briefly describe their behavior, ecology, and life history, pointing out differences among populations within the California sea lion as well as species differences. Important sources of threats to the populations are mentioned. These were hunting in the past, but are now habitat degradation, including pollutants and bycatch through net entanglements.

Variation in life history traits is directly linked to individual fitness. This interplay is complicated by environmental perturbations in an unpredictable habitat. To maximise fitness, individuals react to environmental changes by reallocating resources between maintenance, growth and reproduction. Disentangling these factors is complicated as traits are interlinked by trade-offs between current reproduction and future survival and reproduction. This study provides first estimates of life history traits and trade-offs of a tropical apex predator, the Galapagos sea lion (Zalophus wollebaeki), in an unpredictable habitat, the Galapagos archipelago. Thirteen years of individual data on birth mass, early growth and offspring, and environmental data allowed the examination of factors influencing reproductive performance of adult females and calculation of pupping rates. Females became primiparous between ages 4 and 9. Neither oceanographic nor body condition in the females’ first year of life influenced age at primiparity. Age at primiparity had no effect on a female’s birth rate, on average one pup every 2 years. Sex of a pup did not influence the subsequent inter-birth interval, but first-year pup survival lengthened it. Until age 6, females showed lower birth rate (

Research on animal personality explains the coexistence of distinct behavioural phenotypes within a species and demonstrates limits to individual plasticity. However, the mechanisms guiding the lifelong development of personality should receive more attention, because many elements of personality are emergent properties of interactions between the environment and an individual's genetic background. In these interactions, mechanisms (e.g. genetic regulatory networks, epigenetic processes and neuroendocrine regulation) influencing personality may be modified. An approach integrating proximate mechanisms with a view of lifelong personality development will crucially improve understanding stability, plasticity and inter-individual variability of personalities and clarify the effects of selection on the phenomenon.

Behavioural differences between individuals are often found to be consistent across contexts and/or over time, although recent studies suggest that ontogenetic processes and learning might influence personality. During ontogeny, environmental influences may play an important role in shaping an individual's personality as well as its physiology. Seasonal changes are ubiquitous and known to influence development. To study developmental plasticity, of behaviour and physiology in the wild cavy (Cavia aperea), we manipulated the photoperiod in a fully crossed match-mismatch design by simulating spring and autumn photoperiod until weaning and subsequently moving half of the animals into the mismatching photoperiod. We found developmental plasticity in behavioural and physiological traits before and after sexual maturation for growth, resting metabolic rate and fearlessness. For fearlessness, changes in response to the opposite photoperiod were more pronounced in males than in females. Exploration and boldness were only influenced by early, but not by late photoperiod. No sex differences were found for these two traits. Even though our treatment changed average trait expression, some behavioural traits proved consistent over time, but physiological traits were not. Fearlessness was consistent only in animals that did not change photoperiod during development, whereas exploration and boldness were consistent over time regardless of photoperiodic treatment. Our study shows that in response to a change in photoperiod personality traits differ substantially in developmental plasticity.

Females of many pinniped species generally exhibit strong fine-scale philopatry, but it is unclear over what spatial scale this behavior may translate into genetic population structure. We conducted a population genetic survey in the Galapagos fur seal, Arctocephalus galapagoensis, an endangered pinniped endemic to a small geographic range in the northwest of the Galapagos archipelago. To assess patterns of genetic diversity levels and population differentiation, we analyzed part of the mitochondrial control region (mtDNA) and 18 microsatellites DNA markers. We detected similar levels of genetic diversity to many other pinniped species (h = 0.86, pi = 0.012, A = 7.44) despite severe anthropogenic exploitation in the nineteenth century and recurrent population crashes due to recent climatic perturbations associated with El Nio Southern Oscillation events. We further found remarkably strong fine-scale matrilineal population structure, with 33.9 % of the mtDNA variation being partitioned among colonies separated by as little as 70 km swimming distance. In contrast, population structure inferred from nuclear markers was weak. Our findings provide further evidence that natal philopatry can translate into fine-scale genetic population structure in highly mobile species. We discuss the relevance of our results for the fine-scale conservation management of this species with a very restricted geographic range.

The role of ontogenetic processes for the emergence of personality has received only little attention in the past. One reason for the lack of experimental studies on personality development may be that trait consistency over time is one of the cornerstones of the definition of animal personality, whereas, also by definition, ontogeny deals with change over time. Single traits or correlations between traits may be consistent or inconsistent throughout ontogeny; however, the proximate and ultimate causes are not well understood. Environmental factors acting upon individuals during early ontogeny potentially influence personality development substantially. Early environments may severely constrain but also adaptively shape individuals. We examined the personality development of cavies, Cavia aperea, when exposed to increasing and decreasing photoperiod before and after birth. We determined how these predictive environmental cues influenced the development of three behavioural and two physiological traits, their temporal consistency and the correlations between them. We found remarkable plasticity in the development of personality in the cavy, despite a relatively high degree of temporal consistency in most traits. There were stable correlations, some of which became tighter over time, between basal cortisol levels, resting metabolic rate and fearlessness across two different ontogenetic stages. However, we also found that some correlations emerged only after maturation or disappeared over time. Whereas exploration behaviour was tightly correlated with basal cortisol and boldness was correlated with resting metabolic rate, both correlations disappeared in mature animals. Instead, a correlation between exploration and boldness was evident in mature animals. These results call for a broader incorporation of developmental aspects into personality research. (C) 2014 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

The positive relationship between sexual size dimorphism (SSD) and harem size across pinnipeds is often cited as a textbook example of sexual selection. It assumes that female aggregation selected for large male size via male-male competition. Yet, it is also conceivable that SSD evolved prior to polygyny due to ecological forces. We analyzed 11 life-history traits in 35 pinniped species to determine their coevolutionary dynamics and infer their most likely evolutionary trajectories contrasting these two hypotheses. We find support for SSD having evolved prior to changes in the mating system, either as a consequence of niche partitioning during aquatic foraging or in combination with sexual selection on males to enforce copulations on females. Only subsequently did polygyny evolve, leading to further coevolution as the strength of sexual selection intensified. Evolutionary sequence analyses suggest a polar origin of pinnipeds and indicate that SSD and polygyny are intrinsically linked to a suite of ecological and life-history traits. Overall, this study calls for the inclusion of ecological variables when studying sexual selection and argues for caution when assuming causality between coevolving traits. It provides novel insights into the role of sexual selection for the coevolutionary dynamics of SSD and mating system.

Age at maturity is a particularly important life history parameter, as it predicts potential life time reproductive success in many small mammal species. Animals should therefore optimize the timing of maturation by reacting to environmental stimuli that predict future environmental conditions. Photoperiod often reliably predicts ecological conditions. Animals born into a photoperiod indicating favorable conditions (spring, summer) may mature earlier and at a lower weight than animals born into conditions indicating unfavorable conditions (autumn, winter). So far most work was done on small, altricial rodent species and we still lack knowledge about their precocial relatives. Precocial animals are born much further developed than altricials and might show less plasticity in their ontogenetic trajectory than the latter. We tested the influence of photoperiod simulated by increasing (spring) or decreasing (autumn) light in climate chambers on important life history parameters in a medium sized rodent, the highly precocial cavy (Cavia aperea). We wanted to determine whether photoperiod influences timing of maturation and early growth in male cavies and whether patterns of testosterone in blood are reflected by patterns of testosterone metabolites in feces. Males born into simulated spring grew faster and matured at an earlier age than males born into simulated autumn conditions. Patterns of testosterone in blood correlated with testosterone metabolites measured in feces. Male cavies strongly react to predictive photoperiod cues by adjusting growth and timing of maturation as we found previously for females, corroborating the importance of seasonal cues for adjustments of life history. (C) 2013 Elsevier Inc. All rights reserved.

The evolution and maintenance of consistent individual differences, so called animal personalities, have attracted much research interest over the past decades. Variation along common personality traits, such as boldness or exploration, is often associated with risk-reward trade-offs. Individuals that are bolder and hence take more risks may be more successful in acquiring resources over the short term. Cautious individuals taking fewer risks may, on the other hand, live longer, but may also gather fewer resources over the short term. According to recent theory, individual differences in personality may be functionally related to individual differences in cognitive performance (i.e., the way in which individuals acquire or use information). Individual differences in the acquisition speed of cognitively challenging tasks are often associated with a speed-accuracy trade-off. Accuracy can be improved by investing more time in the decision-making process or, conversely, decisions can be made more quickly at the cost of making more mistakes. Hence, the speed-accuracy trade-off often involves a risk-reward trade-off. We tested whether 3 personality traits, boldness, activity, and aggressiveness, are correlated with individual learning, associative learning speed, and behavioral flexibility as assessed by reversal learning in wild cavies (Cavia aperea). We found strong positive relationships between all personality traits and learning speed, whereas flexibility was negatively associated with aggressiveness. Our results support the hypothesis that performance reflects individual differences in personality in a predictable way. (PsycINFO Database Record (c) 2013 APA, all rights reserved).

Amphibious mammal species alternate between foraging at sea and attendance on land. Due to thermoregulatory requirements, they often haul out during the night, making social interactions difficult to observe. We tested the suitability of UHF-proximity loggers for assessing social relationships among Galapagos sea lions Zalophus wollebaeki. To survive periods at sea, proximity loggers were embedded in epoxy. Automatic downloads to receiving stations rendered logger recovery unnecessary. Encounters were logged within a range of 10 m. Logs provided information about interacting individuals as well as time and duration of encounters. 'Received signal strength indicator' values correlated with distance, but were influenced by antenna angle and environmental factors. Laboratory tests and validation in the field demonstrated that the spa- tial resolution corresponded to 2 m. Data needed to be corrected, as single encounters were recorded as multiple logs and reciprocity of loggings between animals was not always achieved. Digital data correlated with observational data, but associations were 4 times more likely to be detected using proximity loggers. Data revealed that non-territorial males frequently associated for extended periods of time, especially during the night and even outside the study colony. The modified proximity logger system proves an excellent tool to determine social structure in situations where direct observation is limited.

Behavioral, physiological, and life-history traits can be modified through interactions with environmental conditions during ontogeny. Until recently, the ecological and social circumstances influencing the developing phenotype have not been investigated in much detail. Nevertheless, they represent an important step in niche construction by which the developing organism can in principle adjust to predictable aspects of its life history. By dynamically changing photoperiod during gestation, we tested how behavioral phenotypes (BPs) and physiology of juvenile cavies (Cavia aperea) adjust to seasonal differences in prenatal photoperiod. The prenatal photoperiod, simulating spring or autumn, led to faster or slower maturation in females but the relative size rank in litter also exerted a major influence on the onset of maturation. In addition, prenatal photoperiod strongly influenced BP and stress response in juvenile animals. Heavy females born into autumn developed a less explorative, more shy BP, whereas heavy females born into spring produced more explorative, bolder BP. Smaller sisters did not differ in the onset of maturation and, correspondingly, we found no differences in the BP. We did not find differences in the BP in males also. Early personality traits, though repeatable, changed over ontogeny to such an extent that early group differences in BP had completely disappeared in adults. Our results indicate high developmental plasticity with respect to predicted optimal life history and suggest long-term plasticity in response to photoperiod.

Size- and age-specific physiological constraints coupled with inexperience make the transition to independent foraging in juvenile divers a crucial period with important consequences for survival, dispersal and future reproduction. Variation in environmental conditions and associated changes in food availability can additionally constrain the juvenile's development to independence. Juvenile Galapagos sea lions Zalophus wollebaeki (GSL) represent an extreme example of these constraints owing to a low growth rate, seasonal variation in food abundance and unpredictable declines in food availability during El Nino events. Time-depth recorder (TDR) data and stable isotope data of delta N-15 and delta C-13 of known age juvenile GSL were analysed to investigate the development of diving and foraging, and a regular year was compared with an El Nino year to determine the effect of environmental change on the foraging behaviour of juvenile and adult GSL. GSL juveniles started diving activity at 12 mo of age and showed distinct juvenile-specific diving strategies that suggest there is an ontogenetic niche shift between juvenile and adult GSL foraging. Successful independent foraging, indicated by a strong decrease in delta N-15 ratio, started considerably later (at 18 mo of age) and was further delayed in the El Nino warm season, indicating there is an even longer dependency on maternal milk during environmentally adverse conditions. Our results suggest that prolonged maternal energetic investment buffers GSL juveniles against the constraints of diving and foraging under environmentally variable conditions and is linked to the low reproductive rate of this species.

Parent–offspring conflict theory posits that parents and offspring differ in the optimal duration of parental care. Accordingly, the timing of the termination of parental care could be contested between parents and offspring. The outcome of this conflict might be related to the degree of parental sensitivity to offspring demand. By cross-fostering zebra finch, Taeniopygia guttata, chicks of different ages among breeding pairs, we examined whether parents continue parental behaviour for a fixed time period, or are sensitive to offspring age. Parents provisioned chicks in the nest for longer when they received younger foster chicks and for less time when they received older foster chicks. All chicks fledged and became independent at the same age. Our results show that zebra finch parents extend the period of parental care in response to protracted demands from their brood.

We aim to stimulate an ontogenetic approach to personalities. We explain the importance of studying development for understanding proximate and ultimate aspects of personality and critically discuss, partly by perhaps provocative statements, our current lack of knowledge and potential approaches to the study of personality development. We first clarify some terminology and argue for a difference between behavioral profiles (BP; at the descriptive level) and personality ( at the explanatory level). We then focus on the issue of temporal stability of personality, arguing that based on evolutionary theory, neurophysiological knowledge, and recent findings, personality is probably less stable than often thought. Next we consider the potential influence of genes, discussing gene by environment correlations and interactions and argue that developmental changes in the regulation of DNA expression are probably more relevant than individual differences in DNA sequence. We end by suggesting perspectives for future research. (C) 2011 Wiley Periodicals, Inc. Dev Psychobiol 53: 641-655, 2011.

The 2008 IUCN (International Union for Conservation of Nature) review of the status of the world’s mammals identified marine mammals (IUCN 2008) as disproportionally threatened and data poor compared to their terrestrial counterparts, and their status was noted as a particular concern (IUCN 2008, Mace et al. 2008, Schipper et al. 2008). The threats faced by marine mammals were identified as being different, with accidental mortality and pollution being dominant threats that superseded habitat loss, which was identified as the principal concern for land mammals. It was suggested that harvesting remained a major threat for half of the marine mammal species in the world. The distribution of marine mammals was described as being concentrated in tropical and temperate coastal platforms and associated with high levels of primary productivity. Threat levels were highest for marine mammals living in the North Atlantic, North Pacific and Southeast Asia. Range size was described as generally declining toward both poles. Although these generalities are of course correct for all marine mammals, it must be recognized that the larger number of species of cetaceans compared to other marine mammal groups (85 cetaceans, the polar bear Ursus maritimus, 4 extant sirenians and 36 pinniped species) biases the conclusions in the assessment for marine mammals to such a degree that a separate summary for the pinnipeds of the world is warranted. Additionally, a species-level assessment masks some important conservation concerns for pinnipeds with species classified as Least Concern actually containing threatened subspecies ( e.g., ringed seals). Finally, and perhaps most importantly, climate change issues were not specifically addressed in the vast majority of marine mammal assessments done for the 2008 IUCN review (IUCN 2008). We present here a complete assessment of the status and threats facing pinnipeds at the subspecies level, integrating the expected impacts of changing patterns of threat due to global climate change.

Information about the age of juvenile pinnipeds is necessary for an understanding of ontogeny-specific patterns and strategies. Exact age determination of juvenile cohorts from wild populations is best achieved through birth observations and subsequent marking, but this involves a considerable time lag during which juveniles mature. A combination of body and teeth measurements of known-age Galapagos sea lion juveniles taken during brief routine captures in the field was used to create age prediction models. Several general linear models (GLMs) produced reliable age estimates for male and female juveniles up to an age of 2 y. Teeth measurements were important predictors of age: male age was best estimated using upper canine length (CL), mass, and girth, while the best predictors for female age were CL, canine width (CW), body length (SL), body mass, and an interaction between CL and CW. The presented method of aging wild unmarked juveniles in the field is applicable during routine captures, requires little equipment, and yields a considerable increase of information for studies involving brief sampling periods in the field. We suggest its adjustment, testing, and application in studies of juveniles of other species.

Development implies a change in allocation of resources from somatic growth to reproduction. In a highly variable environment, growth can vary from year to year thereby influencing the long-term life history perspective. The Galapagos sea lion (Zalophus wollebaeki) lives in a highly unpredictable marine environment in which food abundance varies not only seasonally, but also annually due to El Nino. Galapagos sea lions are restricted to a patch of cold upwelling waters surrounding the archipelago and are closely tied to land as nursing females alternate between foraging at sea and nursing ashore. Therefore, their offspring are especially vulnerable to ocean warming causing reduced food abundance. We found a significant correlation between sea surface temperature (SST) and early growth: Both mass at birth and linear growth within the first 2 mo of life correlated negatively with SST. Absolute mass gain was higher for males, but both sexes gained equally 1.9% of birth mass per day. Until the age of 3 yr male and female juveniles showed similar growth to an asymptotic mass of 40 and 35 kg, respectively. As a consequence of the highly variable environment, the plasticity in growth strategy of Galapagos sea lion juveniles appears wider than that of all other sea lions allowing them to cope with poor conditions.

Understanding reproductive behavior, especially the circumstances surrounding parturition and the events following the first days postpartum, is essential in developing effective conservation strategies for endangered pinnipeds. In the case of the critically endangered Mediterranean monk seal (Monachus monachus), difficulties in documenting events such as parturition are compounded by the very low population numbers and the inaccessibility of the habitat occupied by the species. In this study, the authors report the first observations of parturition for the species from the central Aegean Sea, Greece, in the eastern Mediterranean Sea. Using a state-of-the-art infrared remotemonitoring system, two births were documented, and important information on the total duration of the events; the total duration of attempted suckling; as well as information on the presentation of the pups, their sex, and habitat were recorded. This new information on the reproductive biology of the species in this part of its range outline the importance of suitable reproductive caves for the conservation of the species and the urgency of protecting them. In addition, considering the high cost and logistics of the study, monitoring the species on a large scale to effectively protect it will require the development of new, low-cost, and time-efficient methodologies.

Based on the publicly available genome draft of Cavia porcellus and four other loci described for C. aperea, we characterized 16 microsatellite loci applicable for C. magna and 12 for C. aperea. We designed the primers to be used in a multiplex fluorescence array. The average number of alleles for each locus was 7.4 and the mean expected heterozygosity was 0.67. The use of these markers provides a good framework for population genetics, molecular ecology and other evolutionary studies in these species.

In many environments, photoperiod is a reliable predictor of ecological conditions. Such predictability generally declines towards low latitudes as the yearly cycle becomes less marked. It has been claimed that photoperiodic effects are small in cavies and guinea pigs that reproduce throughout the year. We here investigated photoperiodic influences on the onset of puberty in female cavies (Cavia aperea) and show that photoperiod exerts a major influence. Female pups kept in groups of two matured at about 47 days when born into lengthening (from 10:14 to 12.5:11.5 L:D) and 79 days when born into shortening day length (from 145:9.5 to 12:12 L:D) and kept under identical short day conditions after weaning on day 20 of life (12.25:11.75 L:D). As shown previously, social conditions, especially the presence of an adult male, proved important modifiers of the onset of maturity in females. Differential stress cannot be responsible for the social effects on puberty as social conditions did not affect cortisol levels in young females. We conclude that photoperiod plays an important role in gearing the onset of cavy reproduction to the seasons and that specific male stimuli rather than unspecific effects of stressors accelerate female maturation. (C) 2008 Elsevier Inc. All rights reserved.

Population substructuring is a fundamental aspect of animal societies. A growing number of theoretical studies recognize that who-meets-whom is not random, but rather determined by spatial relationships or illustrated by social networks. Structural properties of large highly dynamic social systems are notoriously difficult to unravel. Network approaches provide powerful ways to analyse the intricate relationships between social behaviour, dispersal strategies and genetic structure. Applying network analytical tools to a colony of the highly gregarious Galápagos sea lion ( Zalophus wollebaeki ), we find several genetic clusters that correspond to spatially determined ‘network communities’. Overall relatedness was low, and genetic structure in the network can be interpreted as an emergent property of philopatry and seems not to be primarily driven by targeted interactions among highly related individuals in family groups. Nevertheless, social relationships between directly adjacent individuals in the network were stronger among genetically more similar individuals. Taken together, these results suggest that even small differences in the degree of relatedness can influence behavioural decisions. This raises the fascinating prospect that kin selection may also apply to low levels of relatedness within densely packed animal groups where less obvious co-operative interactions such as increased tolerance and stress reduction are important.

The processes governing social interactions and the resulting relationships among members of colonially organized animals are largely unknown. Using network analytical tools we investigated fundamental components of social structure in a highly fluid fission-fusion society. We constructed a social network and studied the relative importance of sex and age class, fine-scale site fidelity and male territory distribution in a breeding colony of the Galapagos sealion, Zalophus wollebaeki. The social system was partitioned into a hierarchy with at least three levels. The outermost level of organization was given by a single social network, where all individuals of the population were interconnected. This level split into communities and further into cliques. Sex and age class influenced social structure at the population level, whereas fine-scale site fidelity explained most of the structure found at the community level. None of these assortment variables could account for clique structure, which might therefore be explained in terms of individual preferences, genetic relatedness or a combination of both. Male territories did not form the basic unit of social structure, but appeared simply to be superimposed on the structural backbone formed by females and young. (C) 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Offspring should be selected to influence maternal effort to maximize their own fitness, whereas mothers are selected to limit investment in present progeny. In mammals, this leads to a conflict over the amount of milk provided and the timing of weaning. The intensity and time course of such conflict has so far mostly been investigated experimentally in altricial rodents. However, it is expected that offspring options for conflict will depend on developmental state. We therefore investigated in the highly precocial domestic guinea pig (Cavia aperea f. porcellus) who decides over nursing performance and weaning and how pup state influences these decisions. Specifically, we tested whether a threshold mass of pups predicts weaning time. By exchanging older litters against neonates and vice versa, we produced a situation in which females differed in lactational stage from the cross-fostered pups. Our results indicate that females decide about the timing of weaning, as cross-fostered younger pups were weaned at a much younger age than controls and older pups benefited from continuing lactation of foster mothers. Growth rates did not differ in the treatment groups, and different weaning ages resulted in differing weaning mass refuting the hypothesis that weaning is based on a threshold mass of offspring. This constitutes clear evidence that in a precocial rodent, the guinea pig, decisions about maternal care are primarily determined by maternal state and little influenced by pup state despite the extreme precociality of offspring. We suggest that precocial pups show little resistance to early weaning when food is abundant, as they reach sufficient nutritional independence by the middle of lactation to enable independent survival.

Parent-offspring conflict theory is well supported by theoretical arguments. However, empirical observations are often difficult to interpret and have contradicted one of its most appealing predictions that parent and offspring should disagree over killing of nest or littermates. We present the first examples of deadly conflict between siblings of different cohorts. In Galapagos fur seals (Arctocephalus galapagoensis) and sea lions (Zalophus wollebaeki), mothers often wean their single offspring at 2 years. This leads to a situation where up to 23% of all pups are born while the older sibling is still being nursed. Younger siblings are disadvantaged by being born lighter than neonates without older still dependent siblings. Pups born while an older sib is still dependent grow less in early life (fur seal) and suffer increased early mortality (both species) through direct aggression or scramble competition with the older sibling. This effect is much stronger in years of high sea surface temperature (El Nino) indicating low marine productivity and if the older offspring is a male. In both species, mothers interfere aggressively in this conflict by defending the younger offspring. In years of El Nino, intense resistance to maternal aggression by the older offspring happens frequently in the fur seal. Such resistance against weaning can induce maternal neglect of the newborn. Given substantial year to year variation in offspring growth, maternal aggression forces weaning in the older sibling only if it has reached sufficient size to support itself by foraging. In Galapagos fur seals, pups with older siblings can either represent insurance against loss of older offspring or extra reproductive value.

Lactation is the most energy-intense period in the life of a female mammal. This can cause severe conflict between mother and offspring over the duration of lactation but also between siblings over the amount of milk each pup gets from its mother. Thus, competitive interactions between siblings are expected, and competition is likely to increase with litter size, particularly in species where the number of offspring exceeds the number of teats. We studied sibling competition in the domestic guinea pig (Cavia aperea f. porcellus), which has two teats, but frequently bears litters of up to five pups. By cross-fostering we created non-competition ( control) litters with two pups and competition litters with four pups and observed nursing behaviour on days 5, 10, 15 and 20 postpartum. Pups of larger litters had lower growth rates, indicating increased competition among siblings in these litters. Pups of larger litters had to wait longer for access to a teat and spent less time suckling than pups of smaller litters but ate more solid food instead. Additionally, we manipulated the individual short-term need of pups by separating half of the pups of each litter for 2 h from their mothers before observation. Within a litter, hungry pups achieved access to milk faster and spent more time suckling than non-hungry pups. Pups competed mostly by scramble competition. Aggressive interactions occurred only in large litters. Pups of large litters had higher cortisol levels than pups in small litters. These effects decreased with age as pups became increasingly independent of maternal milk. Pup behaviour appears to fit better with models of scramble competition than with those of honest signalling.

The effects of the direct interaction between hybridization and speciation—two major contrasting evolutionary processes—are poorly understood. We present here the evolutionary history of the Galápagos marine iguana (Amblyrhynchus cristatus) and reveal a case of incipient within-island speciation, which is paralleled by between-island hybridization. In-depth genome-wide analyses suggest thatAmblyrhynchusdiverged from its sister group, the Galápagos land iguanas, around 4.5 million years ago (Ma), but divergence among extant populations is exceedingly young (less than 50 000 years). DespiteAmblyrhynchusappearing as a single long-branch species phylogenetically, we find strong population structure between islands, and one case of incipient speciation of sister lineages within the same island—ostensibly initiated by volcanic events. Hybridization between both lineages is exceedingly rare, yet frequent hybridization with migrants from nearby islands is evident. The contemporary snapshot provided by highly variable markers indicates that speciation events may have occurred throughout the evolutionary history of marine iguanas, though these events are not visible in the deeper phylogenetic trees. We hypothesize that the observed interplay of speciation and hybridization might be a mechanism by which local adaptations, generated by incipient speciation, can be absorbed into a common gene pool, thereby enhancing the evolutionary potential of the species as a whole.

Foraging differentiation within a species can contribute to restricted gene flow between ecologically different groups, promoting ecological speciation. Galapagos sea lions (Zalophus wollebaeki) show genetic and morphological divergence between the western and central archipelago, possibly as a result of an ecologically mediated contrast in the marine habitat. We use global positioning system (GPS) data, time-depth recordings (TDR), stable isotope and scat data to compare foraging habitat characteristics, diving behaviour and diet composition of Galapagos sea lions from a western and a central colony. We consider both juvenile and adult life stages to assess the potential role of ontogenetic shifts that can be crucial in shaping foraging behaviour and habitat choice for life. We found differences in foraging habitat use, foraging style and diet composition that aligned with genetic differentiation. These differences were consistent between juvenile and adult sea lions from the same colony, overriding age-specific behavioural differences. Our study contributes to an understanding of the complex interaction of ecological condition, plastic behavioural response and genetic make-up of interconnected populations.

Within pinnipeds, phocids and otariids show differing maternal care. strategies. Phocids rear young out of body stores in a yearly cycle with a single stay ashore when the mother fasts while lactating, whereas otariids provision their young by repeated foraging trips to sea alternating with brief stays ashore where they suckle their young. In a previous optimality model, these differences have been interpreted as adaptations based on differing energy requirements of large (phocid) and smaller (otariid) species, and the time budget of the large elephant and the much smaller Antarctic fur seal were correctly predicted. Our refined model-extended to pinniped species of all sizes-predicts lactation strategies to shift from attendance cycles to 1-year cycles with increasing body mass and provides an explanation for the finding that phocid pups are weaned at lower relative mass than otariid pups. However, other predictions do not correspond to empirical findings. In particular, the model does not explain the behavior of large otariids and small phocids. Thus, maternal metabolic requirements alone appear insufficient to explain observed lactation patterns. In the light of our results, we discuss more generally the scope and limitations of optimality models when applied in a comparative framework to a group of related species.