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Sex-biased parasitism is found in many species, but the skew to one sex or the other varies and is most likely due to differences in host and parasite behaviour and the intensity of sexual selection. We examined sex-biased parasitism in Richardson's ground squirrels (Urocitellus richardsonii (Sabine, 1822)) and hypothesized that males would be more heavily parasitized than females, as they are larger, have larger home ranges, and display high aggression and fighting during the short mating season, suggesting that they may trade off investment in immunity for higher investment in reproduction. Squirrels were caught during the mating season and examined for endoparasites and ectoparasites. Body mass, condition, and immune measures were recorded. Males had higher nematode prevalence and abundance, whereas females had higher flea prevalence. Males also had lower lymphocytes than females, as well as higher neutrophil to lymphocyte ratios. Females had higher eosinophils and they were in poorer body condition than males. The higher endoparasite loads in males suggests that they may be trading off immunity, whereas higher flea prevalence in females may be due to differences in sociality between the sexes. Our study demonstrates the importance of examining multiple parasite types to understand the factors influencing sex-biased parasitism. Key words: Urocitellus richardsonii, ectoparasites, endoparasites, Richardson's ground squirrels, sex-biased parasitism, immunity. Le parasitisme variant selon le sexe est present chez de nombreuses especes, bien que l'asymetrie vers un sexe plutot que l'autre varie, vraisemblablement en raison de differences de comportement de l'hote et du parasite et de l'intensite de la selection sexuelle. Nous avons examine le parasitisme variant selon le sexe chez les ecureuils de Richardson (Urocitellus richardsonii (Sabine, 1822)) et postule que les males seraient plus intensement parasites que les femelles puisqu'ils sont plus gros, que leurs domaines vitaux sont plus grands et que leur agressivite et leur combativite sont elevees durant la courte periode de rut, laissent croire qu'ils pourraient reduire leur investissement immunitaire au profit d'un investissement accru dans la reproduction. Des ecureuils ont ete captures durant la periode de rut, et leurs endoparasites et ectoparasites ont ete examines. La masse corporelle, l'etat d'embonpoint et des mesures de l'immunite ont ete enregistres. La prevalence et l'abondance de nematodes etaient plus elevees chez les males, alors que la prevalence de puces etait plus grande chez les femelles. Les males avaient egalement moins de lymphocytes que les femelles, ainsi que des rapports neutrophiles:lymphocytes plus eleves. Les femelles avaient plus d'eosinophiles et un moins bon etat d'embonpoint que les males. Les charges d'endoparasites plus elevees des males donnent a penser que ces derniers compromettraient leur immunite au profit d'autres fonctions, alors que la prevalence plus elevee de puces chez les femelles pourrait etre causee par des differences entre les sexes sur le plan de la socialite. Notre etude demontre l'importance d'examiner plusieurs types de parasites pour comprendre les facteurs qui influent sur le parasitisme variant selon le sexe. [Traduit par la Redaction] Mots-cles : Urocitellus richardsonii, ectoparasites, endoparasites, ecureuil de Richardson, parasitisme variant selon le sexe, immunite., Introduction Sex biases in parasite loads are well documented in the literature; however, the sex with the higher parasite loads appears to vary between and even within the species (Krasnov [...]

Predator detection and deterrence are major benefits of sociality for many small mammals, and these benefits may extend to interspecific groups. In southern Africa, Cape ground squirrels (Xerus inauris) often share burrow systems with two species of mongoose, suricates (Suricata suricatta) and yellow mongooses (Cynictis penicillata). Each of these three species lives in highly social groups of conspecifics; for squirrels, this grouping reduces the amount of time spent vigilant and increases feeding. These species are usually very tolerant of one another, and Cape ground squirrels may benefit from the vigilance of suricates and the anti-snake behavior of mongooses; however, this hypothesis has never been tested. I observed Cape ground squirrels near their burrows in the presence and absence of suricates and yellow mongooses to determine if squirrels benefitted from these interspecific relationships. Squirrels spent significantly less time vigilant and more time resting in the presence of suricates, but time spent feeding was not affected. Vigilance was reduced much further by the presence of other squirrels than the presence of suricates. When snakes were present, Cape ground squirrels were actually more active in mobbing the predator than were yellow mongooses or suricates. Thus, there does seem to be some benefit from associating with these other species, but the survival benefits of associating with conspecifics are much stronger.

Cooperative breeding is common among social animals and is characterized by group members that exhibit delayed dispersal from natal group, reproductive suppression, and alloparental care. Mechanisms of reproductive suppression may be mediated through the presence of breeding females, exposure to males and/or resource levels. Initial field studies of Xerus inauris indicate evidence for reproductive delay as first estrus of sub-adult females differs with number of adult breeding female group members. We investigated reproductive suppression in free-ranging female X. inauris by examining behavior and hormone profiles of pre-reproductive and reproductive females to verify inhibition of sexual maturity. Correlations between progestogen profiles and group structure were examined to infer possible mechanisms of inhibition. Preliminary results suggested that reproductive suppression in female Cape ground squirrels is mediated at multiple levels. Reproductive suppression may be costly for dominant breeding females as their reproductive success decreased with increasing group size.

Studies of free-ranging animals often require identifying individuals in a study population in order to obtain detailed data on population dynamics, movement patterns, and behavior. However, capturing and handling animals for identification can be difficult and expensive, and may affect the behavior of the animals being studied. We evaluated the reliability of a non-invasive method of identifying individual polar bears based on whisker spot pattern variations. Digital photographs of the profiles of fifty polar bears (taken in western Hudson Bay) were chosen on the basis of image sharpness and distance to the bear. Paralleling a method of identification and assessment of reliability developed for lions, we divided spot patterns for each bear into characters that corresponded to cells on a regular grid and estimated their overall complexity (i.e., information content). We calculated the probability of occurrence and complexity of each spot pattern based on the individual frequency values of each character. All fifty spot patterns contained enough information to be distinguished from other spot patterns in our study population. These results suggest that individual identification of polar bears in the field using whisker spot pattern variations can be used as a reliable method of non-invasive identification.

In the social species of ground-dwelling sciurids, females live in cohesive, matrilineal social groups. There are many suggested benefits of such cohesive groups, yet in some species of sciurids, reproductive success declines with increased group size. Although resources are the ultimate constraint on group size, parasitism is another more proximate factor that can determine reproductive strategies. We tested the hypothesis that parasites influence behavior in a highly social species of African ground squirrel by experimentally manipulating parasite loads. We trapped and marked all animals in 14 social groups. In addition to the regular handling and measurements, all individuals in seven of the groups were treated for both ecotoparasites (using Frontline) and endoparasites (using ivermectin). Parasite counts were estimated by removing ectoparasites with a flea comb and using fecal floats for endoparasites. We predicted that parasite load would increase with group size, that female body mass would increase after treatment, and that time spent grooming and allogrooming would decrease. Our data support the hypothesis that parasites significantly affect the behavior of this species.

The timing of ovulation, whether an animal is a spontaneous or induced ovulator, plays an important role in the understanding of the evolution of reproductive strategies and social systems within a given species. The Cape ground squirrel, Xerus inauris, is a highly social, non-hibernating ground squirrel found in southern Africa. To determine the method of ovulation in this species, ten males and 15 females were brought into captivity for a period of 15 weeks. Female urine was initially collected in the absence of male stimuli and then in either chemical and visual contact or physical contact with males. The urine was then analyzed for progesterone content using a [sup.125]I radioimmunoassay. The ovaries of six females were also sectioned and mounted to look at follicular development. Hormonal and histological evidence supports the prediction that the Cape ground squirrel is a spontaneous ovulator. This is the first evidence of spontaneous ovulation in a ground-dwelling squirrel.

Characterizing the ecological constraints that influence the structure of social groups is a major task in the study of sociality. In many species, as environmental conditions become more severe or the habitat becomes saturated, the rising costs of independent breeding may increasingly skew reproduction within a social group. The Cape ground squirrel (Xerus inauris) lives in the arid regions of southern Africa and evidence suggests that the social structure of this species may differ in areas with greater rainfall and more vegetative productivity. I compared the group structure of X. inauris in three different sites: a low rainfall (

Polar bears, Ursus maritimus, are widely considered asocial animals. Yet while waiting for the sea ice to form near Churchill, Manitoba, male polar bears engage in play behavior, including rigorous play fighting when temperatures start cool in October and November. These energetically costly play bouts last from 15 seconds to 43 minutes, yet rarely result in injury. We collected detailed observational data in the fall seasons of 2001 and 2002 to examine the functional significance of this play behavior. From vehicles modified for travel on the tundra we recorded (a) body size, (b) use of space and (c) time budgets of individual bears, as well as (d) sizes of aggregations and (e) detailed components of male-male interactions. Play fighting included few aggressive components, comprising

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