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At the Gannet Islands, Labrador, sympatric thick-billed murres ( Uria lomvia (L., 1758)) and razorbills ( Alca torda L., 1758) are slightly sexually dimorphic and have similar intersexual differences in parental roles; females are the main meal providers and males are mostly involved in brooding and chick defence at the breeding site and at sea. The question is whether differences in parental roles influence the foraging behaviour patterns of males and females. Murre females foraged during twilight periods and dived shallower than males. In razorbills, although sex differences were not as clear, females also tended to dive shallower (

We studied female and male parental roles in two sympatric auks, thick-billed murre (Uria lomvia) and razorbill (Alca torda), with initial biparental care at the breeding site and later exclusively paternal care at sea. Our study addressed the following two questions: Why do males accompany chicks to sea?, and How do the sexes allocate parental effort at the breeding site before parental care at sea begins? We tested the hypothesis that males care for chicks at sea because they are in better condition at the time of chick departure as a result of femalebiased parental effort at the breeding site (‘nest’). Breeding success and duration of chickrearing did not differ between the two study years in either species at the Gannet Islands, Labrador. At the breeding colonies, females of both species provided more food (murres: 2.84 ± 0.18 loads day−1; razorbills: 2.02 ± 0.11 loads day−1) to their chicks than males (murres: 2.26±0.12 loads day−1; razorbills: 1.42±0.09 loads day−1), and males spent more time brooding the chicks. These differences were chick-age dependent in both species, with females providing more meals to chicks older than two weeks. Razorbill males spent more time with chicks greater than two weeks old, while murre male’s attentiveness of brooding did not vary with chick age. In both species, males (murres: 3.04 ± 0.3 h day−1; razorbill: 3.30±0.2 h day−1) performed longer foraging trips with meal delivery than females (murres: 1.23 ± 0.4 h/day; razorbill: 2.50 ± 0.4 h day−1). Thick-billed murres showed a consistent diurnal pattern of egg and chick attendance: females were usually found at the breeding site during the day whereas males were found there early in the morning and at night. In contrast, razorbill’s timing of attendance was much more variable and did not differ between sexes. Despite these differences in timing of breeding site attendance between species, males of both species spent twice as much time as females engaged in the defence of the egg or chick at the breeding site, which suggest male-biased capability of protecting the chick at departure. Overall our data indicated different female and male parental roles at the breeding site but not a female-biased allocation of time, energy and risk as predicted. In fact, males seem to provide equal if not more parental effort than females prior to the time of colony departure. We propose that the patterns of parental roles found between sexes is the result of a chain of events favouring male involvement in chick brooding and care at sea.

The purpose of this study was to examine the importance of body size and body composition as determinants of conditional mating tactics exhibited in male grey seals. We combined behavioral observations with measures of energy expenditure and success on 42 known-age individuals during the breeding seasons of 1997–2001 at Sable Island, Canada. Males with a large body mass arrived at the breeding grounds with more body fat and body energy and catabolized less body protein than smaller males. Males consumed 1.9 6 0.2 MJ day � 1 , and those with a smaller percentage of body fat had higher rates of food energy intake. The amount of body energy on arrival was positively correlated with the duration of the breeding period. Males that exhibited the primary mating tactic of consortship were heavier, had absolutely more body fat and body energy, and sustained breeding longer than those males that did not exhibit the primary tactic. Amongst all males, body mass showed a quadratic relationship with the number of female consorts mated and the estimated number of pups sired. Thus, intermediate-sized males mated with the most consorts and achieved the highest success. Intermediate body size may be optimal during breeding due to greater agility in male combat. Body size was an important determinant of mating tactics used by male grey seals. A large body size provided an energetic advantage of greater endurance while an intermediate body size may provide greater competitive ability in acquiring consortships. Key words: body size, conditional mating tactics, endurance rivalry, energetics, Halichoerus grypus, pinnipeds, reproductive behavior. [Behav Ecol]

Studies using molecular markers have shown that some grey seal males may be gaining success through exhibiting alternative mating tactics. We estimated the probability of fertilization success of grey seal males exhibiting the primary tactic of female defence and one alternative tactic of mating with departing females on Sable Island, Nova Scotia, Canada, during the breeding seasons of 1997-2002. Although the fertilization rate of the primary tactic (27-43%) was greater than that of the alternative tactic (10-12%), these low rates indicate the potential fitness value of alternative mating tactics in this size-dimorphic pinniped species.

We studied the foraging behaviour of endangered Humboldt penguins (Spheniscus humboldti) to examine general foraging patterns, sex differences in foraging behaviour, and the reasons for incidental catches in fishing nets. Humboldt penguins foraged diurnally and typically made short, shallow dives within 30 m of the surface. Males and females made overnight (lasting 25.8 ± 3.4 h; mean ± SD) and day (10.4 ± 2.0 h) trips when they departed the colony to forage. Overnight trips were more common (68.2% of all trips) and were associated with a significantly greater amount of foraging time. Males dived to greater maximum depths than females but did not differ in other diving parameters, including foraging time, foraging effort, and proportions of day and overnight trips made. Adults may maintain their body condition during chick rearing by making a mixture of overnight and day trips. The two foraging periods observed during overnight trips may function to feed both the adults and the chicks, whereas the single period observed during day trips may function to accommodate the rate of provisioning required by the chicks. We suggest that both males and females would be protected from incidental catches in fishing nets if commercial fisheries avoided setting surface nets at night and setting nets between 0 and 30 m depth during the day in areas where penguins forage and transit.

Predators face decisions about which prey to include in their diet in order to maximize fitness. The foraging tactics used to capture prey and the resulting profitability of prey influence these decisions. We present the first evidence of prey-dependent foraging tactics and prey profitabil- ity in a free-ranging pinniped. We studied 39 adult male harbour seals Phoca vitulina at Sable Island, Nova Scotia using an animal-borne video system. Each male wore the camera system for 3 d during which 10 min video samples were recorded every 45 min from 06:00 h, resulting in approximately 3 h of videotape per male and a total of 1094 capture attempts of identified prey. Males foraged mainly on sand lance Ammodytes dubius and flounders (Pleuronectids), but salmonid and gadoid fishes were occasionally pursued. Foraging tactics differed among and within prey types based on differ- ences in prey behaviour. Sand lance was both a cryptic prey, when in the bottom substrate, and a con- spicuous schooling prey. Seal swimming speed, handling time and capture success differed between cryptic and conspicuous sand lance. The highest capture success and handling time was recorded for flounders. Estimated profitability, i.e. net energy intake per unit time, also differed with prey type and prey size. Our results suggest that diet selection may have important implications on the foraging energetics of pinnipeds.

Marine animals equipped with data recording devices sometimes show changes in their foraging behaviour, which can indicate an adverse effect of the instrument. We attached time-depth recorders (TDRs) and radio-transmitters to study foraging behaviour in Humboldt Penguins Spheniscus humboldti and observed an increase in the duration of foraging trips. We suggest that further tagging of this endangered species be approached with caution since this increase in trip duration may negatively affect reproductive and foraging success.

When closely related species breed in sympatry, and where hybrids have lower fitness, reinforcement theory predicts that selection should favour mechanisms that reduce the probability of interspecific matings. If this situation arises among species that exhibit resource defence polygyny where males and females of different species reside in the same territories, there may be some conflict between mate choice based on territory-holding ability (sexual selection) and mate choice for correct species. We investigated this in a population of fur seals where three species are sympatric and where some females breed in the territories of heterospecific males, and where interspecific matings and hybrid pups are observed. The territorial status of males and the birthing sites of females were determined during daily observations, as were the movements of males and females, the location of matings and mating partners. DNA extracted from skin samples was used to determine paternities using DNA fingerprinting and the mtDNA genotype of individuals. Individuals were also classed on the basis of species-typical phenotype. We found that extra-territory inseminations (ETIs) were significantly more prevalent (67%) when territorial males and resident females were of different phenotype than when of similar phenotype (27%), but mtDNA genotype had no effect on the rate of ETIs. ETIs were probably by males with the same phenotype, as pups born to these females in the following season had the same phenotype as their mothers, suggesting they were not hybrids. These results suggest that within the resource defence polygynous mating system of these sympatric fur seals, female mate choice is more influenced by male phenotype than genotype. Contrary to our predictions, our study indicates that potential conflict between mate choice based on sexual selection and species recognition is unlikely, because females have some capacity to discriminate between males both within and between species on phenotypic traits additional to those under sexual selection. Although at least 25% of the pups born in this study were hybrid, this study can only support reinforcement theory if hybrids have reduced fitness. The fitness of hybrids among the species studied is currently unknown.

We tested the hypothesis that kin selection may play a role in fostering behaviour in grey seals. Fostering frequency varied among three colonies, ranging from 3% to 28%. Band-sharing coefficients (S) of DNA fingerprints, from two multilocus probes, were used to predict relatedness (r). Mean r did not differ between foster mother-pup pairs and the expected r = 0 for presumed unrelated female-pup pairs. Likewise, mean r between fostered and filial pups compared to r between presumed unrelated pups within the same beaches did not differ. Mean S values of presumed unrelated pups on different beaches within the two smallest colonies were indistinguishable, indicating that there is not increased variation in relatedness in small colonies. These results suggest that kin selection does not play a significant role in the maintenance of grey seal fostering behaviour.

Vocalizations of individual Hawaiian monk seal pups, Monachus schauinslandi, do not have unique attributes that enable females to recognize their own offspring. Despite low aggregation density during pupping, aggressive encounters are common between females with pups. Fostering is prevalent and may reflect confusion over the identity of pups following aggressive encounters between females. All pup vocalizations were simple in structure and contained true harmonics. The coefficients of variation revealed considerable variance in vocalization structure within pups. Controlling for age, multivariate analyses of variance revealed significant differences among pups in vocalization attributes. Significant developmental changes occurred in vocalization structure for some pups but not for others. Discriminant function analysis suggested that it would be difficult for females to distinguish between the vocalizations of pups. The results of experiments conducted in the field showed that females did not discriminate between filial and alien pups by voice. In addition, females tended not to foster pups that had vocalizations similar to those of their own offspring. Thus, females seem to be unable to recognize their pups by voice. The apparent lack of vocal recognition of pups may contribute to the high frequency of fostering in this species.

Lactation strategies in the two largest families of seals have been characterized as a phylogenetic dichotomy, with sea lions and fur seals (Otariidae) exhibiting foraging cycles and true seals (Phocidae) a strategy of fasting. We show that a lactating phocid, the harbor seal, Phoca vitulina, has a foraging cycle similar to that of otariids. Time-depth recorders attached to lactating harbor seal mothers revealed that 9 of 11 females began bouts of diving, averaging 12–40 m, by mid-lactation (12 days). During the remainder of lactation, females made an average of seven diving trips, lasting about 7 h. They returned to the rookery during the interval between successive bouts to nurse their pups. Diving was more frequent during daylight than at night and diving bouts increased in duration as lactation progressed. The diving behavior of females that had weaned their pups and previously collected data from stomach lavage, suggest that the bouts of diving represent successful foraging. We propose that the lactation strategy of the harbor seal is intermediate to that of the otariids and other phocids studied. The harbor seal has a foraging cycle like the otariids, but typically resembles other phocids in length of lactation, rate of mass gain in pups, and in milk fat content. As harbor seals are among the smallest phocids, and only slightly larger than most otariids, it seems likely that maternal size constrains the amount of stored energy harbor seal females can bring to the rookery, forcing them to start feeding during the lactation period.

Publisher Summary Sea lions are members of the family Otariidae. There are presently seven sea lion species in five genera. They originated in the Northeast Pacific region, sharing a common ancestor with fur seals. Although the fossil record for sea lions is poor, it appears they crossed into the Southern Hemisphere about 3 million years ago. Sea lions do tend to be larger than fur seals, with both groups exhibiting substantial differences in body mass, and smaller differences in body length, between males and females, a phenomenon known as sexual dimorphism. The ability to dive and stay underwater is an important characteristic for all marine mammals, including sea lions. Although large lung volume is important for diving animals, the lung volume for sea lions is equally proportional to their body size as to other marine mammals and even terrestrial mammals. They follow a lifestyle typical to that of all the otariids, with some characteristics common to all seals. They are long-lived, have delayed sexual maturation, and have physical and social sexual bimaturation, with males maturing more slowly than females. The status of sea lion populations is variable. The Japanese sea lion has not been sighted since the 1970s and is now considered extinct. According to the International Union for Conservation of Nature (IUCN), three species—the California, Australian, and southern sea lions—are currently considered as being at low risk of extinction. The sea lion species for which there is greatest concern at present and is listed as endangered and at high risk of extinction by the IUCN is the Steller sea lion.

Hooded and harbor seals are unique among true seals (family Phocidae) in that the lanugo (fetal pelage) is typically shed in utero. Shedding had occurred in all newborn hooded seals examined off the Labrador coast (n = 62) and in 94% of newborn harbor seals on Sable Island, Nova Scotia (n = 110), although in one-fifth of the latter the molt was incomplete. In hooded seals the shed hair in the amniotic sac was organized into tightly woven disks, whereas in harbor seals the shed hair formed a loose mat with no evident structure. We examined hair masses in the intestines of pups of both species but could find no evidence that the intestines were involved in hair disk formation. We argue that fetal shedding, like prenatal blubber deposition, is an adaptation enabling newborn pups to enter cold water without adverse consequences. This ability allows the use of pupping substrates that are unstable or regularly inundated with water.

Although harbour seals may not recognize their relatives, relatives could be chosen preferentially for fostering (i.e. kin selection) if harbour seals display natal philopatry coupled with breeding site fidelity, and thus kin are clustered within the colony. We used behavioural and genetic data to investigate population structure within the Sable Island breeding colony and to test whether harbour seals tend to foster related pups. Adult females on Sable Island showed a high level of breeding-colony site fidelity but low levels of within-colony site fidelity both within and between years. Similarly, although lactating females showed a clumped distribution, group composition was highly variable, suggesting that this study colony was not composed of groups of related animals. DNA fingerprint data supported the hypothesis that female distribution within the colony was not correlated with genetic relatedness. Furthermore, the mean DNA band sharing among foster dyads did not differ significantly from that for unrelated animals. These results indicate that among harbour seals, related pups are not usually chosen preferentially for fostering and hence, kin selection is not likely to be influencing the occurrence of this behaviour. Copyright 1999 The Association for the Study of Animal Behaviour.

Substantial advances have been made in the past two decades toward a theory of mating systems (Orians, 1969; Selander, 1972; Trivers, 1972; Jarman, 1974; Emlen and Oring, 1977; Bradbury and Vehrencamp, 1977; Kleiman, 1977; Wittenberger, 1979; Thornhill and Alcock, 1983; Rubenstein and Wrangham, 1986). These recent efforts have focused on the interplay between sexual selection and environmental factors that determine temporal and spatial dispersion of males and females (e.g. resource distribution, predation pressure). Increased information on behavioural reproductive strategies has led to examination of theory both within and between taxa to assess the breadth of its applicability (see Bradbury and Vehrencamp, 1977; Ostfeld, 1985; Rubenstein and Wrangham, 1986 for reviews of different taxa). A comparison between antelope and emballonurid bats has shown that the form of mating systems in both groups is set within the bounds of female dispersion, which is strongly related to food distribution (Bradbury and Vehrencamp, 1977). On the other hand, factors such as habitat type and body size are good predictors of social dispersion and mating strategies in antelopes but not bats.

Adult males of the grey seal, Halichoerus grypus (Fab.) (Phocidae), display the large snout conspicuously in threats. The male's snout has probably evolved through sexual selection as a visual display organ, as in some other extant phocids: the hooded seal, Cystophora cristata (Nilsson) and the two species of elephant seals, Mirounga (Gray). This may also be true of the extinct desmatophocid Allodesmus Kellogg. Cephalic display organs in the form of long tusks have also evolved twice in the Odobenidae (walruses). Comparable display structures do not occur in the Otariidae (fur seals and sea lions). However, the massive neck of adult male otariids is important in undirected static-optical threat displays, especially at long range, and in some kinds of short-range threats. Also, adult otariids show sexual dimorphism in facial appearance, which varies interspecifically.Pinniped species in which large mature males have prominent, constant-growing cephalic display structures show fluid spacing among rutting males, and much agonistic communication at the water surface and on land or ice. This correlation may reflect selective pressures on males to affirm social status repeatedly, through displays which communicate their age (hence strength and experience), and their resource-accruing abilities.

Breeding activity budgets of male gray seals were estimated to determine how they are fine tuned to changing demands and to determine whether or not the limited body reserves produced by fasting act to minimize energetically demanding activities. Behaviors were divided into nonsocial and social activities with each category including both active and inactive behaviors. The overall frequency of social behavior did not change throughout a male's tenure but aggressive behavior decreased while sexual behavior increased. Even though resting accounted for the greatest proportion of activity, males that were most active had the greatest copulatory success, suggesting that fasting does not place severe limitations on their activity levels.

We describe an unusual mating system, observed in a land-breeding colony of Grey seal, Halichoerus grypus, in the western Atlantic. Males and females begin to visit the breeding beach about a week before the season begins, but none stay ashore for long until the first pup is born. The cows are gregarious, probably return to the same part of the beach to give birth from one year to the next, and tend to remain in the general vicinity of the birth site during their two and a half week sojourn ashore. Within these limits, however, they are quite mobile, and the size, location and composition of the temporary aggregations which they form vary from one day to the next. The cows become thinner and more sedentary as oestrus approaches, but otherwise they give no overt signs of receptivity. The males do not defend territories, nor do they form dominance hierarchies. Instead, they compete for tenure, the right to remain within the shifting population of females. Tenured bulls directly test the receptivity of nearby cows from time to time, and they continually manoeuvre in ways which maximize their chances of being next to cows which are either in oestrus or likely to become so in the near future. Bulls which fail to establish themselves amongst females try to intercept cows as they are leaving for the sea at the end of their season, but their reproductive success, estimated in several ways, is significantly lower than that of bulls with tenure. The system would be adaptive for seals which breed on the pack ice, but it is unique amongst land-breeding pinnipeds. If, as some circumstantial evidence suggests, Grey seals were originally pack-ice breeders, the persistence of such a system in a land-breeding colony raises some interesting questions about the plasticity of mating behaviour.

Resting metabolic rate and body temperature of California sea lion pups (Zalophus californianus: Otariidae) were measured for 39 animals (12,000 g, mean body mass) captured from breeding areas on San Nicolas Island, California. These 3-5-wk-old pups had a mean specific resting metabolic rate of 0.780 ± .010 ml O₂ g⁻¹ h⁻¹, which is 2.380 times the value predicted by Kleiber for adult mammals with similar body mass; mean body temperature was 37.8 ± .08 C. This level of metabolism is similar to those reported for young seals (Phocidae). The heat-transfer coefficient (h) was 24.6 times that predicted from body mass, and it appeared that some individuals were on the verge of hypothermia at ambient air temperatures below 19 C. Although high metabolic rates are typically associated with high growth rates in terrestrial mammals, high heat loss associated with relatively poor insulation in sea lion pups may require allocation of relatively large amounts of energy to thermoregulation (=maintenance), thus limiting t...

Aggression of female grey seals Halichoerus grypus toward conspecifics was studied during the pupping and mating season on Sable Island, N.S. The responses of 65 individually identified females with pups toward known males and females were recorded throughout each female's stage of lactation. Female aggression varied both quantitatively and qualitatively as a function of the sex of an approaching animal. Males were threatened more often than females even though females outnumbered males. The likelihood of females threatening other females was affected by the location of the threatening female's pup, but aggression towards males was not affected by the pup's position. Females responded aggressively less often in the second half of lactation, when both weaning of the pup and oestrus occur, than in the first half. They were also more likely to threaten transient males than tenured males. However, a male approaching or mounting a female, whatever his status, was more likely to be challenged by another male if the female threatened him than if she did not. These challenges generally interrupted a male's approach or mount and hence a potential copulation. The results are consistent with the hypothesis that female aggression during the lactation period helps to protect the pup and increases the likelihood that a female mates with a dominant male. This latter function may be viewed as a form of mate choice.

Based on scant empirical data, the mating system of the hooded seal (Cystophora cristata) has been variously characterized as monogamous or polygynous. To evaluate the hypothesis that female hooded seals are clustered to a degree that would facilitate polygyny, we collected data on the spatial dispersion of female and male seals on the ice floes off the Labrador coast. While flying from a ship at the edge of the seal herd to a study site within the herd, we recorded each sighting of female seals as a "solitary female" or a "cluster of females" (using an approximate 10 body length radius to differentiate these conditions). The numbers of males near females were also recorded. Nearest-neighbor distances were obtained during on-ice transects. The frequency of nearest-female-neighbor distance classes peaked at 6–10 seal body lengths (one body length = 1.9–2.6 m) and then declined to distances of greater than 25 body lengths. About 40% of 357 females with pups (or 22% of 279 sightings of seals) were in clusters consisting of two or more mother–pup pairs; the maximal cluster size observed was five. The majority of females or clusters of females had a single male in attendance (54% of 245 sightings). Females in the central part of the herd were both clustered and attended by males more often than were females at the periphery. Observations of a few marked males suggested that some took up positions near additional females when their original female companions departed. These results are consistent with the hypothesis that the spatial pattern of hooded seals should facilitate polygyny.