Female Yearlings Research Articles

Environmental drivers of demography and potential factors limiting the recovery of an endangered marine top predator

AbstractUnderstanding what drives changes in wildlife demography is fundamental to the conservation and management of depleted or declining populations, though making inference about the intrinsic and extrinsic factors that influence survival and reproduction remains challenging. Here we use mark–resight data from 2000 to 2018 to examine the effects of environmental variability on age‐specific survival and natality for the endangered western distinct population segment (wDPS) of Steller sea lions (Eumetopias jubatus) in Alaska, USA. Though this population has been studied extensively over the last four decades, the causes of divergent abundance trends that have been observed across the wDPS range remain unknown. We developed a Bayesian multievent mark–resight model that accounts for female reproductive state uncertainty. Annual survival probabilities for male pups (0.44; 0.36–0.53), female yearlings (0.63; 0.49–0.73), and male yearlings (0.62; 0.51–0.71) born in the western portion of the wDPS range, estimated here for the first time, were lower than those in the eastern portion of the wDPS range, estimated as: male pups (0.69; 0.65–0.74), female yearlings (0.76; 0.71–0.81), and male yearlings (0.71; 0.65–0.78). There was a higher proportion of young female breeders in the western portion of the range, but overall natality was lower (0.69; 0.47–0.96) than in the eastern portion of the range (0.80; 0.74–0.84). Additionally, pup mass had a positive effect on pup survival in the eastern portion of the range and a negative effect in the western portion of the range, potentially due to earlier weaning of heavier pups. Local‐ and basin‐scale oceanographic features such as the Aleutian Low, the Arctic Oscillation Index, the North Pacific Gyre Oscillation, chlorophyll concentration, upwelling, and wind in certain seasons were correlated with vital rates. However, drawing strong inferences from these correlations is challenging given that relationships between ocean conditions and an adaptive top predator in a dynamic ecosystem are exceedingly complex. This study provides the first demographic rate estimates for the western portion of the range where abundance estimates continue to decline. These results will advance efforts to identify factors driving regionally divergent abundance trends, with implications for population‐level responses to future climate variability.

Age‐ and sex‐specific survival of the Gunnison's prairie dog (Cynomys gunnisoni)

AbstractAge‐ and sex‐specific survival rates are essential for understanding animal population dynamics and discerning environmental influences on population parameters. To date, little research has been done on age‐ and sex‐specific survival of the Gunnison's prairie dog (Cynomys gunnisoni), a colonial ground‐dwelling squirrel inhabiting the sagebrush ecosystem of the southwestern United States. To discern impacts of the year of study, age, sex, and reproductive status on survival, we conducted a capture‐mark‐recapture analysis on a previously collected long‐term dataset of a population of Gunnison's prairie dogs (n = 2508) from 1989 to 1995. We implemented two models: age‐cohort Cormack–Jolly–Seber (CJS) models (to examine survival by age, sex, and year) and multistate mark‐recapture models (to analyze survival by age and year, as well as breeding status). Females had higher apparent survival than males. Yearlings had a low apparent survival rate (0.288 ± 0.022, [±SE]) compared to juveniles (0.461 ± 0.019) and adults (0.482 ± 0.055). Less than 50% (48.0 ± 2.7) of female yearlings successfully weaned litters each year. Yearling survival rate was lower than other highly social prairie dog species that do not reproduce as yearlings, suggesting that there may be a cost to reproduction. We also constructed a postbreeding matrix population model and associated elasticity analysis, which indicated that the reproductive output of yearlings was the most significant potential driver of population growth. Our findings provide more nuanced estimates for age‐ and sex‐specific survival in this species than were previously available and also more broadly inform linkages between demography and sociality in prairie dogs.

Observations of a Remnant Population of Translocated Pronghorn Near Hillside, Arizona

We monitored the persistence of a remnant population of pronghorn (Antilocapra americana) near Hillside, AZ, over an 11-year period from May 2008 through December 21, 2019. Originally consisting of three bucks, two does, and one female yearling, the last pregnant doe was seen March 13, 2014, and the last fawn was seen on November 10, 2014. Only one buck was seen after June 17, 2014, and no males after July 7, 2018. The last pronghorn seen were three does on a follow-up survey April 3, 2021. Although the possibility exists of animals immigrating or emigrating from the 78 km2 study area, we did not document such behavior during our study. With no overt attempts at management the population doubled, before losing four animals following a May 2014 Palmer Drought Severity Index (PDSI) of -4.09. The persistence of this population through 2021 is attributed to low adult mortality and a greater recruitment of females than males. The low percentage of available habitat utilized suggests an adequate carrying capacity. The disappearance of this population is attributed to inbreeding depression and low recruitment due to genetic bottle-necking. The Hillside population was too small and too isolated to survive without periodic translocations. Although we frequently observed coyotes during our surveys, predation was not considered the principal factor in the population's demise.

Extreme climate event promotes phenological mismatch between sexes in hibernating ground squirrels

Hibernating ground squirrels rely on a short active period for breeding and mass accrual, and are thus vulnerable to extreme climate events that affect key periods in their annual cycle. Here, we document how a heatwave in March 2012 led to a phenological mismatch between sexes in Richardson’s ground squirrels (Urocitellus richardsonii). Females emerged from hibernation and commenced breeding earlier in 2012 relative to average female emergence. Although males had descended testes and pigmented scrota, it appeared that not all males were physiologically prepared to breed since 58.6% of males had non-motile sperm when breeding commenced. Body condition, relative testes size, and the relative size of accessory glands were significant predictors of sperm motility. Males with non-motile sperm had smaller accessory glands than males with motile sperm. There was no decrease in the number of juveniles that emerged in 2012 or female yearlings recruited in 2013, nor did juveniles emerge later than other years. The impact of this heatwave on male ground squirrels emphasizes the importance of assessing the consequences of climate change on the breeding success of hibernating species in both sexes, since the different sensitivity to external cues for emergence led to a mismatch in timing under this event.

Risky movements? Natal dispersal does not decrease survival of a large herbivore.

Natal dispersal is assumed to be a particularly risky movement behavior as individuals transfer, often long distances, from birth site to site of potential first reproduction. Though, because this behavior persists in populations, it is assumed that dispersal increases the fitness of individuals despite the potential for increased risk of mortality. The extent of dispersal risk, however, has rarely been tested, especially for large mammals. Therefore, we aimed to test the relationship between dispersal and survival for both males and females in a large herbivore. Using a radio‐transmittered sample of 398 juvenile male and 276 juvenile female white‐tailed deer (Odocoileus virginianus), we compared survival rates of dispersers and nondispersers. We predicted that dispersing deer would experience greater overall mortality than philopatric deer due to direct transfer‐related risks (e.g., vehicular collision), indirect immigration‐related mortality attributable to colonization of unfamiliar habitat, and increased overwinter mortality associated with energetic costs of movement and unfamiliarity with recently colonized habitat. For both male and female yearlings, survival rates of dispersers (male = 49.9%, female = 64.0%) did not differ from nondispersers (male = 51.6%, female = 70.7%). Only two individuals (both female) were killed by vehicular collision during transfer, and overwinter survival patterns were similar between the two groups. Although dispersal movement likely incurs energetic costs on dispersers, these costs do not necessarily translate to decreased survival. In many species, including white‐tailed deer, dispersal is likely condition‐dependent, such that larger and healthier individuals are more likely to disperse; therefore, costs associated with dispersal are more likely to be borne successfully by those individuals that do disperse. Whether low‐risk dispersal of large mammals is the rule or the exception will require additional research. Further, future research is needed to evaluate nonsurvival fitness‐related costs and benefits of dispersal (e.g., increased reproductive opportunities for dispersers).

Age- and sex-dependent vigilance behaviour modifies social structure of hunted wild boar populations

Abstract Context Human activities in general, and hunting in particular, often have significant impacts on the behaviour of wildlife through the anti-predator behaviours they evoke. Wild boar populations are rapidly expanding worldwide and their population densities are increasing. Aims To examine hunting effects in combination with different land-use factors on the behaviour and social structure of wild boars (Sus scrofa) in Israel. Specifically, to examine differences in vigilant behaviour and social structure in agricultural areas (hunting permitted) and nature reserves (hunting prohibited). Methods Motion-triggered cameras were installed to record wild boars’ social structure and vigilance behaviour along movement trails. Age and sex of individual wild boars were identified, as were the size and structure of their social groups, and hunting in each of the studied areas was quantified. Key results Results indicated significant differences in the vigilance behaviour of wild boars between agricultural areas and nature reserves. In agricultural areas, adult females were significantly more vigilant (P < 0.001) compared with adult males (P = 0.150). Additionally, in these areas there were significantly more adult males and fewer females leading family groups (P < 0.001). Furthermore, male yearlings were significantly more vigilant in agricultural areas (P < 0.001) compared with female yearlings (P = 0.164). Male yearlings tended to roam significantly more with family groups in agricultural areas compared with nature reserves, where they tended to roam alone or in groups (P = 0.029, P = 0.035). Conclusions These results indicate social and behavioural differences in wild boars between agricultural areas and nature reserves, suggesting that hunting may have a substantial impact on their social structure and behaviour. Implications Overall, the findings support the behavioural and social consequences of human hunting. Long-term implications of altered behavioural and social responses should be considered in management and conservations strategies. For instance, the high proportion of male yearlings in family groups in agricultural areas in autumn (October–December, mating season) may offer young males early access to reproductive females, even within the same social group. This may eventually lead to an increase in the reproductive potential of female wild boars.

Lifetime Sex‐Specific Moose Mortality During an Intentional Population Reduction

ABSTRACTWhere elevated harvest of ungulates is a priority, managers benefit by understanding how various sources of mortality affect the age and sex structure and trend of ungulate populations. Prior studies reported a long period (1997–2014) of moose (Alces alces gigas) nutritional stress from overabundance in our study area, an intentional 31% reduction in moose numbers using liberal harvests of females (2004–2012), and low bear (Ursus spp.) predation and high moose harvest densities relative to other largely roadless systems with moose, bears, and wolves (Canis lupus). In this paper, we detailed management findings after describing causes and rates of mortality from 226 female and 164 male moose radio‐collared at 9 months of age (1997–2008) and followed through life (1997–2019) and throughout the population reduction. We listened for mortality signals on radio‐collars 1–2 times/month when snow cover was complete and 2–4 times/month when snow cover was incomplete. Upon hearing a mortality signal, we investigated mortality sites usually within 24 hours via helicopter. Excluding hunter‐caused mortality, we estimated 28% annual mortality for male yearlings versus 17% for female yearlings, then low annual mortality rates (0–4%) to 84 months of age for males and 96 months of age for females, and gradually increasing annual mortality rates thereafter. Most (83%) male moose ≥24 months of age died from hunters; minor causes included wolves (8%), malnutrition or disease (5%), grizzly bears (U. arctos; 2%), and accidents (2%). Most female moose ≥24 months of age died from wolves (37%) or hunters (33%); minor causes included malnutrition or disease (15%), grizzly bears (10%), and accidents (5%). The proportion of radio‐collared females killed by hunters varied depending on numbers of permits issued to hunters; the kill rate of females ≥24 months of age was 58% during the initial 4 years of the 9‐year reduction, moderated at 29% during the final 5 years of the reduction, and was only 7% for all other study years. We attributed 32% of hunter kills to illegal harvest and unrecovered hunter kills. Hunters played a key role in the intentional population reduction by harvesting prime‐age and near prime‐age male and female moose that rarely died from other sources of mortality compared with calf, yearling, and older moose. Restricting general season hunters to primarily harvesting prime‐age and older male moose with antler spreads ≥127 cm did not appreciably reduce harvest of adult males. Male moose 2.0–5.3 years of age rarely died from non‐hunter causes and were largely harvested at older, prime ages (5.3–8.3 yr of age). Yearling moose of both sexes died primarily from wolves, with wolves selecting more for males. By using liberal harvests of female moose to reduce the population, managers improved moose nutrition and reproduction, met mandates for elevated harvests, and may have avoided a reoccurrence of a previous precipitous decline in moose numbers that was initiated by overabundance and extreme snow depths. © 2019 The Wildlife Society.

Social group dynamics and composition of managed wild vicuñas (Vicugna vicugna vicugna) in Jujuy, Argentina

The vicuna is a high Andean wild camelid that lives year-long in groups. We analyzed the social organization of 98 marked vicunas after capture and live shearing, focusing on group composition, spatial patterns, territoriality and habitat use. The social units analyzed were families, bachelor groups and solo animals. Location fixes of 54 males and 36 females were registered over a 2-year period, and home range was estimated. All females belonged to family groups, and 8–12 month yearlings changed their home ranges prior to first reproduction at 2 years. Female yearlings dispersed to a new family group, while male yearlings dispersed to a bachelor group. Solitary males appeared during the interval between leaving bachelor or family groups, and vice versa. Our study showed that vicuna polygyny was based on female grazing area requirements. Females that stayed with the same males were defined as loyal, and had a mean 18.9 ha home range. Females that changed both to a different family and male; and grazed over the same home range size, were considered disloyal. Family groups selected the habitat that had a low stratum and the highest coverage of palatable plants, while bachelors used their habitat randomly.

Early transfer of mated females into the maternity unit reduces stress and increases maternal care in farm mink

Mated mammals on farms are typically transferred to another housing environment prior to delivery. We investigated whether the timing of this transfer – EARLY (Day −36), INTERMEDIATE (Day −18), or LATE (Day −3) relative to the expected day of birth (Day 0) – affects maternal stress, maternal care and the early kit vitality in farmed mink. We hypothesized that early transfer is beneficial for mink mothers and their offspring in comparison to intermediate or late movement closer to delivery, being the current practice in the commercial production. We used 180 double mated female yearlings in three equally sized groups (n=60): (i) ‘EARLY’, transfer to maternity unit immediately after the end of the mating period, March 23; (ii) ‘INTERMEDIATE’, transfer in the middle of the period, April 10; (iii) ‘LATE’, transfer late in the pregnancy period, April 25. Data collection included weekly determination of faecal cortisol metabolites (FCM) and evaluation of maternal care: nest building, in-nest temperature, plus kit-retrieval behaviour, kit mortality and growth day 0–7 postpartum. We document that mated mink females build and maintain a nest at least 1 month prior to delivery when transferred to an environment with free access to nest building material. During the weeks before delivery, INTERMEDIATE females had 50% higher FCM concentrations than the other two groups (P=0.002), indicative of stress. After delivery, late moved females had, in average, 2.7°C colder nests compared to early moved females (P=0.002). Additionally, the mortality in group LATE tended to be higher (P=0.085) in affected litters (N=92). Kits from early transferred females displayed less vocalization (17% vs. 40–41% in the two other groups, P=0.015), when tested away from the nest. This indicates enhanced offspring vitality from early moved females. In conclusion, transfer into the maternity unit early after mating, rather than later during the pregnancy period, reduces stress and increases maternal care in farm mink.

Social Dominance Hierarchies and Phenotypic Correlates of Dominance in Captive Groups of the Grey-cheeked FulvettaAlcippe morrisoniain Taiwan

Dominance hierarchies usually form quickly among avian foraging groups because they are beneficial to most individuals by reducing conflict. Several characteristics that correlate with dominance rank have been identified in birds, but most of these conclusions rely on studies of temperate species. Hence, we studied whether captive group members of a subtropical species, grey-cheeked fulvetta Alcippe morrisonia, form social dominance hierarchies when competing for food during the non-breeding season. We also investigated whether sex, age, body condition and fat score were related to an individual's dominance rank which was established by counting aggressive interactions in six captive groups of nine individuals each. In all groups, linear dominance hierarchies were formed whereby yearlings dominated over adult birds, and individuals with a better body condition were also more dominant, while sex and fat score had no discernable effect. Male yearlings had significantly higher body masses and body condition indices than male adults, while female yearlings had significantly higher body masses, body condition indices and fat scores than female adults. However, there were no significant differences between male and female yearlings or adults for any of these variables. We suggest possible reasons for the dominance of yearlings, such as captive conditions or the higher body weight of yearlings.

Buğday, Mısır ve Karabuğday Samanları İçeren Rasyonlarla Beslenen Dişi Tokluların Performanslarının Belirlenmesi

As well as cereal straw, the use of maize straw in ruminant feeding has been increasing as the feed shortage widens. In addition, cultivation of buckwheat with high straw yield potential is becoming widespread. Thus, performance of 15 female Karya yearlings fed with ration containing wheat, maize or buckwheat straws were compared. The yearlings fed either containing wheat, maize or buckwheat straws in three total mixed rations (30% straw in dry matter) that were consisted of, maize silage, concentrate and cracked maize, formulated to provide 150 g daily live weight gain for 21 d. Total mixed rations was prepared based on the nutritive value of wheat straw. Prior to feeding trial yearlings were acclimatized to their respective feed for a period of 14 d. Straws were included in total mixed rations following the chopping at 1-2 cm. Daily live weight gain and dry matter intake of yearlings fed with mixed ration containing wheat, maize or buckwheat straw were 88, 85 and 135 g/d (P=0.10) and 954, 931 and 1078 g/d (P=0.09), respectively. However, crude protein intake of yearlings (g/d) fed with the ration containing buckwheat straw 14% higher than yearlings fed with the ration containing wheat or maize straw. It was concluded that performance of yearling fed with ration containing buckwheat straws was superior to performance of yearlings fed with ration containing wheat and maize straw, while performance of yearling fed with ration containing wheat or maize straw was similar.

First evidence of long-distance dispersal of adult female wild boar (Sus scrofa) with piglets

Using GPS telemetry and ear tagging, we monitored wild boar sounder (a 2-year sow, a female yearling and eight piglets) captured in northern Slovenia. Five months after the capture, the sounder left its home range and first travelled 100 km west, to the three-border area between Slovenia, Austria and Italy, and from there toward southeast. The sow and three piglets were shot 2 months after start of dispersal 60 km from the capture site and in-between travelled at least 500 km. At least one piglet continued dispersal after the death of the sow, and the yearling split from the sounder during dispersal. This is the first documented case of long-distance dispersal of adult female wild boar with piglets. Several arguments suggest that long-distance dispersal of female wild boar is more common than previously reported in the literature. For wild boar and other species with predominant male dispersal, data on occasional far-dispersing females like presented here are important for understanding biology of species (e.g. metapopulations, rate of population expansion, local sex and age structure of population) and for management including control of diseases.

Patterns of parasite prevalence and individual infection in yellow‐bellied marmots

AbstractPatterns of infection and prevalence result from complex interactions between hosts and parasites, the effects of which are likely to vary by species. We investigated the effects of age, sex and season on the likelihood of individual infection, and the effects of host population size, sex ratio and age structure on parasite prevalence. We capitalized on data from a long‐term study of yellow‐bellied marmots Marmota flaviventris potentially infected with fecal–orally transmitted intestinal parasites (Ascaris sp., Eimeria spp. and Entamoeba sp.), ectoparasitic fleas Thrassis stanfordi, and a flea‐ and louse‐transmitted blood parasite Trypanosoma lewisi. Patterns of individual‐ and group‐level infection varied widely by parasite. Yearlings were more likely to be infected with Tr. lewisi and Ascaris. Yearlings were also slightly more likely than adults to have Eimeria, but female yearlings had higher infection levels than female adults, while male yearlings had lower infection levels than male adults. Entamoeba infection decreased as the season progressed. Adults and males were more likely to be infected with Th. stanfordi. Ascaris prevalence increased with colony size. There were no significant relationships between colony size and prevalence of Entamoeba, Tr. lewisi, Eimeria or Thrassis. There was a small, but significant positive correlation between male‐biased sex ratio and prevalence of fleas. The host population's age structure affected the prevalence of infection of Ascaris and Eimeria. Overall intestinal parasite diversity increased with colony size. Taken together, our results show a great deal of variation in the likelihood of individual infection and patterns of parasite prevalence in marmots.

Evaluation of the Captive Care and Post-Release Behavior and Survival of Seven Juvenile Female Hawaiian Monk Seals (Monachus schauinslandi)

Extremely poor juvenile survival in the endangered Hawaiian monk seal (Monachus schauinslandi) is primarily caused by prey limitation and continues to drive the population decrease in the Northwestern Hawaiian Islands (NWHI). In 2006-2007, a pilot project was conducted to determine whether temporarily providing nutritional supplementation and protection from predation would enhance the survival of juvenile monk seals. Seven female seals, two of which were rare fraternal twins, were included in the captive care (CC) project. Six weanling seals gained weight commensurate with their duration in captivity, 89 to 297 d, with weight gains of 31 to 143% initial body weight, and were released at Midway Atoll. The seventh seal, a female yearling, died 23 d after being admitted from complications associated with malnutrition and stress. The CC and three control seals were instrumented with satellitelinked GPS dive recorders to monitor post-release behavior and survival as part of an assessment of the project’s success. Satellite tags transmitted between 37 and 311 d. Initially, the CC seals foraged closer to shore, used less of the atoll, and dove to shallower depths ( 60 m and > 4 min). Over the course of several weeks, most of the CC and control seals were foraging in a similar fashion. These results demonstrate that following a brief acclimation period, captive-fed monk seals are capable of foraging normally postrelease. However, none of the CC seals were alive as 2-y-olds, whereas two of the control seals were alive in 2010 as 4-y-olds. Although post-release survival was poor in the current study, with a more suitable release location, an expanded captivefeeding program could be a useful tool to salvage the reproductive potential of Hawaiian monk seals in the future.

Evaluation of steroid hormones anabolic use in cattle in Croatia

Natural sex hormones are part of the endocrine system and are found in animal biological material. On analysis of residual substances with anabolic effect and detection of their abuse, it is necessary to know the physiological levels of these hormones to be able to differentiate physiological concentrations from the illegal use of anabolics. The hormone concentrations exceeding the physiological ones, found on monitoring for illegal substance use, would point to the abuse of these substances for anabolic purpose. In the present study, concentrations of the natural hormones 17?-estradiol, progesterone and testosterone were determined in bovine plasma according to animal age and sex. Natural hormone concentrations were determined using quantitative validated ELISA methods in plasma samples from cattle of different breed composition collected at several farms in Croatia during the 2006-2009 period. Methods validation showed good mean recovery and repeatability (approx. 75-87%), demonstrating the methods efficiency in determination of 17?-estradiol, progesterone and testosterone level in cattle plasma, respectively. The level of sex hormones was statistically significantly higher in yearling plasma as compared with calf plasma (P<0.05). The highest levels of 17?-estradiol (0.03?0.01 ng/mL) and progesterone (4.87?1.63 ng/mL) were recorded in female yearlings, and of testosterone (9.44?5.47 ng/mL) in male yearlings. Results showed the steroid hormone levels to vary with animal age and sex, indicated that illegal use of anabolic substances could not be suspected in none of the study animals.

Sex-differential effects of inbreeding on overwinter survival, birth date and mass of bighorn lambs

Although it is generally expected that inbreeding would lower fitness, few studies have directly quantified the effects of inbreeding in wild mammals. We investigated the effects of inbreeding using long-term data from bighorn sheep on Ram Mountain, Alberta, Canada, over 20 years. This population underwent a drastic decline from 1992 to 2002 and has since failed to recover. We used a pedigree to calculate inbreeding coefficients and examined their impact on lamb growth, birth date and survival. Inbreeding had a substantial effect on female survival: for a given mass in September, the probability of overwinter survival for inbred female lambs was about 40% lower than that of noninbred ones. Contrary to our expectations, inbred female lambs were born earlier than noninbred ones. Earlier birth led to inbred female lambs being heavier by mid-September than noninbred ones. There was a nonsignificant trend for inbred female yearlings to weigh more than noninbred ones. A stronger mass-dependent viability selection for inbred compared to noninbred female lambs may explain why surviving inbred females were heavier than noninbred ones. Survival of male lambs was not affected by inbreeding. Sex-differential effects of inbreeding may be a general pattern in sexually dimorphic mammals, because of sex-biased maternal care or sexual differences in early development strategies.

Play Partner Preferences in Siberian Ibex, Capra ibex sibirica

A study of social play in Siberian ibex kids at the Chicago Zoological Park revealed clear play partner preferences. Male kids played much more among themselves than with female kids and elicited more withdrawals by play partners than did ♀♀. ♂♂ and ♀♀ in mixed-sex bouts, played mostly with similarly aged partners. Male kids played a substantial amount with female yearlings; female kids did not. These differences support a motor training explanation of social play because they suggest that young ♂♂ in this sexually selected species discriminate in favor of partners with whom they can play forcefully.

Female philopatry and male dispersal in a cryptic, bush‐dwelling antelope: a combined molecular and behavioural approach

In most mammals, females are philopatric while males disperse in order to avoid inbreeding. We investigated social structure in a solitary ungulate, the bushbuck Tragelaphus sylvaticus in Queen Elizabeth National Park, Uganda by combining behavioural and molecular data. We correlated spatial and social vicinity of individual females with a relatedness score obtained from mitochondrial DNA analysis. Presumed clan members shared the same haplotype, showed more socio-positive interactions and had a common home range. Males had a higher haplotype diversity than females. All this suggests the presence of a matrilineal structure in the study population. Moreover, we tested natal dispersal distances between male and female yearlings and used control region sequences to confirm that females remain in their natal breeding areas whereas males disperse. In microsatellite analysis, males showed a higher genetic variability than females. The impoverished genetic variability of females at both molecular marker sets is consistent with a philopatric and matrilineal structure, while the higher degree of genetic variability of males is congruent with a higher dispersal rate expected in this sex. Evidence even for male long-distance dispersal is brought about by one male carrying a haplotype of a different subspecies, previously not described to occur in this area.

A test of the social cohesion hypothesis: interactive female marmots remain at home.

Individuals frequently leave home before reaching reproductive age, but the proximate causes of natal dispersal remain relatively unknown. The social cohesion hypothesis predicts that individuals who engage in more (affiliative) interactions are less likely to disperse. Despite the intuitive nature of this hypothesis, support is both limited and equivocal. We used formal social network analyses to quantify precisely both direct and indirect measures of social cohesion in yellow-bellied marmots. Because approximately 50 per cent of female yearlings disperse, we expected that social relationships and network measures of cohesion would predict dispersal. By contrast, because most male yearlings disperse, we expected that social relationships and cohesion would play a less important role. We found that female yearlings that interacted with more individuals, and those that were more socially embedded in their groups, were less likely to disperse. For males, social interactions were relatively unimportant determinants of dispersal. This is the first strong support for the social cohesion hypothesis and suggests that the specific nature of social relationships, not simply the number of affiliative relationships, may influence the propensity to disperse.

Mortality and reproductive patterns of wild European polecatsMustela putorius in Denmark

Despite its relative abundance and wide geographical range, the population dynamics and reproductive biology of the European polecatMustela putorius Linnaeus, 1758 are largely unknown as to the wild living. We therefore investigated age and reproductive status of 239 Danish polecats primarily killed in traffic or trapped during 1998–2004. Males comprised two third of all individuals in all age groups. Based on a static life table, apparent annual mortality was 68% during the first year of life, 33% during the second year and 65% from the third year in both sexes. The mean (± SE) litter size of 5.95 ± 0.62 (n = 18), estimated from placental scar counts, was significantly lower than litter sizes at birth reported for captive individuals but consistent with litter sizes reported for wild polecats in Russia. Female yearlings conceived at the same rate and produced litters of the same size as older individuals.Males had spermatozoa in their testes from February through August. Testes mass peaked in April and May, ie the same period when most females conceive. A lower prevalence of individuals with spermatozoa in yearlings suggests that most males postponed sexual maturity to two years of age.