Subadult Females Research Articles

Rediscovery of the critically endangered Nelson's small-eared shrew ( Cryptotis nelsoni), endemic to Volcán San Martín, Eastern México

A series of 12 shrews was collected in May 1894 by Edward W. Nelson and Edward A. Goldman on Volcan San Martin Tuxtla, Veracruz, Mexico, at 4,800 feet. A year later, C. Hart Merriam described these specimens as a new species, Blarina nelsoni (Merriam 1895). The holotype (skin and skull, USNM 65437), a subadult female, was deposited along with the entire series at the National Museum of Natural History in Washington, D.C. Merriam (1895) reported that this shrew was known only from the isolated volcano of Tuxtla, and that was common in the forest on the mountain ranging up to the extreme summit at 5,400 feet. This species was later transferred to the genus Cryptotis as C. nelsoni by Miller (1912); Choate (1970) treated it as a distinctive subspecies of C. mexicana-C. mexicana nelsoni and named the type locality as ‘‘Volcan San Martin’’. Recently, Woodman and Timm (1999) recognized Nelson’s small-eared shrew as a distinctive species, C. nelsoni, after examination of the 12 known museum specimens, and Carraway (2007) concurred with this taxonomic status. Choate (1970) after extensive review of all specimens of Middle American Cryptotis in the world’s collections stated that no specimens of C. m. nelsoni had been obtained since the original series

Spatial and temporal patterns of problem polar bears in Churchill, Manitoba

Human–bear interactions near the town of Churchill, Manitoba occur annually because the Western Hudson Bay polar bear population spends 4–5 months on-land each year when the sea ice melts completely. Significant changes have occurred in the Hudson Bay ecosystem and in the bear population as a result of climate warming; however, how these changes may have influenced human–bear interactions near Churchill is unclear. This study examined the temporal and spatial patterns of 1,487 problem bears captured in the Churchill area from 1970 to 2004. We also examined the relationship between problem bears and environmental variables as well as the Nunavut harvest. The number of individual problem bears caught near Churchill varied from 10 to 90 individuals per year and increased over time. Subadult males comprised 39%, subadult females 23%, adult males 18%, females with young 14%, and solitary females 6% of captures. Bears that became problem individuals were in closer proximity to the Churchill area. Nutritional stress and a northward shift in the distribution of the bears that spend the summer on-land in northeastern Manitoba may account for the increase in problem bear numbers. The date of sea ice freeze-up, which is getting progressively later, was the best predictor explaining the annual variation in the occurrence of problem bears. These results provide an understanding of how a warming climate may directly impact polar bear behaviour. This information may allow wildlife managers to predict relative levels of human–bear interactions and thereby implement effective management strategies to improve human safety and the conservation of polar bears.

Social dynamics of the golden snub‐nosed monkey (Rhinopithecus roxellana): female transfer and one‐male unit succession

Among primates that form multilevel societies, understanding factors and mechanisms associated with the movement of individuals between groups, clans, and one-male social units offers important insight into primate reproductive and social strategies. In this research we present data based on an 8-year field study of a multilevel troop of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in the Qinling Mountains of China. Our study troop contained 78-126 individuals, and was usually organized into 6-8 one-male units (OMU). The majority of OMUs were composed of networks of unrelated females and their offspring. We found that 59.7% (43/72) of subadult and adult females in our study troop transferred between OMUs (n=66) or disappeared (n=7) from the troop. In the majority of cases, two or more females transferred together into new OMUs or troops. In R. roxellana, new OMUs formed in several ways. During 2001-2008, 16 adult males appeared in the study troop. Over this period, we observed 13 different males who became harem leaders either by taking over an existing harem or by attracting females from other OMUs into their harem. We also observed four OMUs from a neighboring troop to successfully immigrate into the study troop. The number of individuals in these newly immigrated OMUs was significantly smaller than that number of individuals in resident OMUs. During harem formation, fighting between adult males was rarely observed, and female mate choice appeared to play a crucial role in harem male recruitment and replacement. These results suggest that golden snub-nosed monkeys are organized in a nonmatrilineal social system. Female mate choice and possibly incest avoidance appear to play important roles in female transfer, male tenure, and OMU stability.

Spatial Habitat Use Patterns of Sea Otters in Coastal Washington

Sea otter (Enhydra lutris kenyoni) movements, home range, and activity budgets were described from data collected during very-high-frequency radiotelemetry studies of 75 individuals on the outer coast of Washington State between 1992 and 1999. Sea otters were located at least once per week from 22 accessible sites along the coast. Over the 7-year study period, range expansion occurred from the core range north and east into the Strait of Juan de Fuca (SJF) as well as southward on the outer coast. Forty-three percent of the sea otters moved into the SJF at least once, most often in winter, using habitat that had not been occupied by sea otters since their extirpation 100 years ago. All sea otters spent portions of their time in the vicinity of Cape Alava, and many animals demonstrated consistent periodic seasonal shifts between specific portions of the coastline over several years. Ninety-five percent annual linear home ranges differed between sex and age classes. Adult males used the largest amount of coastline (50 km 6 9 SD) and subadult females used the least (24 6 9 km). Both adult males and females demonstrated high seasonal periodicity in range use in summer and winter. Twenty-four–hour time budgets in the core portion of the range revealed on average sea otters spen t4 1 % 6 14% SD of the time foraging and 45% 6 13% of the time resting (age and sex classes pooled). Adult and subadult female sea otters were most frequently found resting and foraging close to shore (,1,000 m) and in shallow water (0–10 m), whereas adult and subadult males rested and foraged .1,000 m offshore and at depths between 10 and 30 m. Given current rates of population growth and observed mobility, sea otters in Washington have high potential for range expansion into unoccupied habitat such as Grays Harbor, Willapa Bay, the SJF, or along Vancouver Island.

Benefits of family reunions: Social support in secondary greylag goose families

Social interactions are among the most potent stressors. However, social allies may diminish stress, increase success in agonistic encounters and ease access to resources. We studied the role of social support as a major mechanism for individual stress management in families of free-ranging greylag geese ( Anser anser). Greylag geese are long-term monogamous, live in a female-bonded social system, and fledged offspring stay with their parents until the next breeding season (‘primary families’). Should parents then fail to fledge young, subadults might rejoin them in summer after molt is completed (‘secondary families’). We have previously shown that primary greylag goose families reap benefits from active social support in agonistic encounters, and also excrete lower levels of immuno-reactive corticosterone metabolites (CORT, ‘passive social support’). Here we investigated how far active and passive social support continues in secondary goose families. Although we found that active support in agonistic encounters was almost absent in secondary families, subadult male geese won an increased number of agonistic encounters due to the mere presence of their secondary family. Particularly adult and subadult females benefited from passive social support through decreased CORT, whereas males did not. Decrease in the hormonal stress response during challenging situations, induced by social allies, may help the females' long-term energy management, thereby improving the odds for successful future reproduction. We discuss whether joining a secondary family may be an alternative tactic for young geese towards optimizing their start into a complex social life.

Home range size and daytime habitat selection of leopards in Huai Kha Khaeng Wildlife Sanctuary, Thailand

Leopards ( Panthera pardus) are endangered in South East Asia yet little is known about which resources need to be secured for their long-term conservation or what numbers of this species this region can support. This study uses radio telemetry to investigate seasonal variation in habitat selection and home range size of Leopards in Huai Kha Khaeng Wildlife Sanctuary, Thailand. Over a five year period, 3690 locations were recorded from nine individuals. The mean ± standard error of fixed kernel home range size for six adult females was 26 ± 8.2 km 2, for two adult males was 45.7 ± 14.8 and for two sub-adult females was 29 km 2 ± 5.5. Adult female wet and dry season home range sizes did not differ significantly. One adult male showed an increase in home range size from dry to wet seasons. Estimated density was 7 adult females/100 km 2, which suggests 195 adult female leopards living in Huai Kha Khaeng alone, thus highlighting the larger Western Forest Complex’s potential contribution to leopard conservation. Compositional analysis of second and third order habitat selection suggested mixed deciduous and dry evergreen forest types, flat slope and areas close to stream channels are important landscape features for leopards. These results can help formulate a much needed conservation strategy for leopards in the region.

Mate competition and reproductive correlates of female dispersal in a polygynous primate species (Rhinopithecus roxellana)

Different mating systems in group-living animals have characteristic behavioral correlates that are primarily related to mate competition. Mate competition may push individuals to selectively make dispersal decisions for the purpose of maximizing of opportunities for reproduction. The Sichuan snub-nosed monkey (Rhinopithecus roxellana) is a polygynous primate species endemic to China. We provide the first data on female dispersal in a free-ranging group of R. roxellana in the Zhouzhi National Nature Reserve, Qinling Mountains, China. Both adult and subadult female dispersal occurred. Immigration/emigration rates of adult females are higher than those of subadult females. Mate competition is one apparent driving force behind adult female dispersal, and inbreeding avoidance is the possible proximate factor influencing subadult female dispersal. Adult female R. roxellana employ various reproductive strategies related to dispersal, which may increase their reproductive success.

Fluttering wing feathers produce the flight sounds of male streamertail hummingbirds

Sounds produced continuously during flight potentially play important roles in avian communication, but the mechanisms underlying these sounds have received little attention. Adult male Red-billed Streamertail hummingbirds (Trochilus polytmus) bear elongated tail streamers and produce a distinctive 'whirring' flight sound, whereas subadult males and females do not. The production of this sound, which is a pulsed tone with a mean frequency of 858 Hz, has been attributed to these distinctive tail streamers. However, tail-less streamertails can still produce the flight sound. Three lines of evidence implicate the wings instead. First, it is pulsed in synchrony with the 29 Hz wingbeat frequency. Second, a high-speed video showed that primary feather eight (P8) bends during each downstroke, creating a gap between P8 and primary feather nine (P9). Manipulating either P8 or P9 reduced the production of the flight sound. Third, laboratory experiments indicated that both P8 and P9 can produce tones over a range of 700-900 Hz. The wings therefore produce the distinctive flight sound, enabled via subtle morphological changes to the structure of P8 and P9.

Relationship between age and activity varies by sex in titi monkeys (Callicebus cupreus)

Motor activity increases during development and typically peaks before reproductive maturity. Males may become more active than do females, and this sex difference in activity may be a mechanism contributing to sex-biased dispersal. The generality of the link between sex differences in activity and sex differences in dispersal would be strengthened with evidence of greater female, as compared to male, activity during development in a species with a female bias in dispersal. Titi monkeys are a good model for such an investigation because subadult females leave their natal group at an earlier age than do subadult males. This study examines whether developing female titi monkeys become more active with age than do developing male titi monkeys. Locomotor activity of 13 female and 8 male captive titi monkeys was measured as they matured from initial ambulatory independence (6 months of age) to reproductive maturity (24 months). Increased activity of females was associated most strongly with increasing age. Increased activity of males, however, was associated most strongly with repeated testing. Compared to maturing males, greater activity of maturing females may underlie the earlier dispersal of female titi monkeys that has been reported.

Males of a subsocial spider choose among females of different ages and the same reproductive status

Most sexual preference studies test female choice between different males or test male choice between females with different reproductive status, but few studies test male preference towards females of different ages within the same reproductive status. In subsocial spiders, males can share the nest with subadult and adult females of different ages. We exposed a male of Anelosimus cf. studiosus to three kinds of females simultaneously: a subadult female, a recently moulted female and a mature adult female (both virgins) comparing male preferences and female interactions. Males courted mature and recently moulted females indiscriminably, but preferentially mated with mature females, while subadult females were not courted. Mature females did not interfere with male courtship towards other females whereas some recently moulted females unsuccessfully attempted to interfere with male courtship towards mature females. In spite of these interferences, no female-female fighting was observed. Taking into account the fact that males court and pseudocopulate with subadult females in uni-female nests, this research using multi-female nests suggests that male preferences show plasticity according to the social context. The preference for copulation with mature females could be due to possible mechanical problems associated to the moult, constraining attempts by males to mate with recently moulted females. This hypothesis and our findings suggest that male may recognize female state and age of adulthood.

Intragroup aggression, fission–fusion dynamics and feeding competition in spider monkeys

Scramble competition is related to animals depleting resources before others can use them, whereas contest competition is associated with the monopolization of resources and food-related aggression. One hypothesized major benefit of fission–fusion sociality is the reduction of scramble feeding competition between community members. We studied intragroup aggression in a community of spider monkeys. Despite seasonal variation in food availability, we found no seasonal difference in aggression rates, which, in combination with a basic lack of aggression among adult females, suggests that fission–fusion dynamics may reduce not only scramble, but also the intensity of contest competition. There were, however, numerous attacks from adult females towards subadult females, especially new immigrants. This aggression, although it occurred mainly during feeding, may not reflect contest competition. Instead, it may be used by resident females to limit scramble competition at the community level, which is ultimately affected by the number of community members. The aggressive harassment of subadult females by long-term resident females can be a means to encourage dispersal of natal subadult females and discourage immigration of new subadult females who are both potential future resource competitors.

Social competence is reduced in socially deprived rhesus monkeys (Macaca mulatta).

Rhesus monkeys deprived for some period from their mother have often served as a model for the effect of adverse rearing conditions on social competence in humans. Social competence is the capacity to react in a species-specific way to social interactions. The current study assesses whether early deprivation from peers also affects the rates of behavior and social competence in rhesus monkeys. This was studied in groups of rhesus monkeys with different rearing conditions: subadult females that were mother-only reared during their first year of life and subsequently housed with peers were compared with subadult females from five naturalistic social groups. Socially deprived monkeys showed higher rates of submission and stereotypic behaviors than socially reared individuals. In addition, they show socially incompetent behavior, since they react with agonistic behavior to nonthreatening social situations. The results suggest that this socially incompetent behavior is rooted in a general feeling of anxiety toward group companions. The authors hypothesize that anxiety negatively affects social information processing, which results in socially incompetent behavior.

The influence of oestrous swellings on the grooming behaviour of chimpanzees of the Budongo Forest, Uganda

Allogrooming among primates has been suggested as a strategy for enhancing reproductive success, by allowing males to enhance their proximity to oestrous females, or by influencing female choice through the development of affiliative relationships with males. Female chimpanzees have swollen anogenital regions signalling receptivity and by adapting their grooming investment accordingly, males could increase their copulatory success whilst females may increase chances of copulations with preferred males. Five and a half years of data from chimpanzees in the Budongo Forest, Uganda, were examined to investigate how sexual swellings influence grooming behaviour between males and females of different age classes. Based on the availability of oestrous females, significantly less grooming than expected occurred between anoestrous females and adult males, as well as between adult (anoestrous and oestrous) females and subadult males, but significantly more grooming than expected occurred between oestrous females and adult males or subadult males. Both oestrous adult and subadult females devoted more time to grooming interactions with adult males than did anoestrous females. Grooming interactions between adult males and oestrous adult females were initiated and terminated significantly more often by males, but those between anoestrous subadult females and adult males were initiated significantly more frequently by females.

Survival and Cause-specific Mortality of a Protected Population of River Otters In Minnesota

Determining causes of mortality and estimating survival rates can provide insight into the status of species for which population trends are not well understood. From Apr. 2002–May 2004 we radio-marked and monitored 39 (13 adult males; 6 subadult males; 8 adult females; 12 subadult females) river otters (Lontra canadensis) in the upper Mississippi River watershed to document causes of mortality, and to evaluate the effects of season, age and sex on survival of river otters in southeastern Minnesota. Further, we assessed the relative importance of demographic parameters to population growth using a projection matrix, which incorporated reproductive data with our observed survival estimates. Human induced mortalities, including accidental captures by fur-harvesters targeting other species (n = 6) and vehicle collisions (n = 1), accounted for the majority of deaths while natural mortality was low (n = 1). Annual survival of females was 0.680 (SE = 0.099) and was 0.946 (SE = 0.052) for adult males. Elasticity of adult female survival was 3.1 times higher than subadult survival, 2.7 times higher than juvenile survival and 2.7 times higher than the sum of elasticity for subadult and adult female reproduction. River otters and other furbearers need to be monitored to assess population status, and management should be responsive to ensure persistence of populations experiencing intentional and/or accidental harvest.

Impact of Male Takeover on Intra-Unit Sexual Interactions and Subsequent Interbirth Interval in Wild Rhinopithecus roxellana

Data were collected on sexual interactions before and after a male takeover of a one-male unit (OMU) of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in the Qinling Mountains, China. The original unit consisted of an adult male, 2 adult and 2 subadult females, 2 female juveniles and a single infant. Following the takeover, the new resident male copulated with 1 adult female, which was not lactating. Subsequent to the disappearance of her infant, the second (lactating female) entered breeding condition and began to solicit copulation with the new resident male. The subadult females also engaged in matings with the new male. The new resident male was observed mating, on 3 occasions, with females in 2 other OMUs. These are the first observations of sexual behaviour in free-ranging Sichuan snub-nosed monkeys after an OMU takeover. Sexual interactions play an important role in establishing relationships between the new male and resident females in the OMU.

Experience leads to preference: experienced females prefer brush-legged males in a population of syntopic wolf spiders

Sexual selection has long been recognized as a potential contributor to the divergence in reproductive characters that ultimately leads to speciation. Schizocosa ocreata and Schizocosa rovneri wolf spiders embody a classic example of species divergence resulting from such sexual selection, as they are reproductively isolated by courtship behavior alone. Here, we characterize a newly discovered population of wolf spiders in which brush-legged males (sensu S. ocreata) and non-ornamented males (sensu S. rovneri) are found syntopically. Mitochondrial sequence data (cytochrome oxidase subunit 1) indicate that the 2 male forms are not reciprocally monophyletic. We exposed subadult females from this mixed population to courtship advances from either brush-legged or non-ornamented males. Experienced females mated significantly more with brush-legged males, whereas inexperienced females showed no mating distinction. In essence, we demonstrate that females from this population will differentially choose between males of 2 distinct forms based on prior experience. Specifically, experience leads to a preference for brush-legged males. We also show that brush-legged males are more sexually aggressive than non-ornamented males. This study highlights the importance of prior experience on subsequent mate choice and has potential implications regarding the extent to which experience can influence polymorphism maintenance and/or species divergence and the evolution of secondary sexual traits.

Defining and identifying sustainable harvests of resources: Archaeological examples of pinniped harvests in the eastern North Pacific

Summary Archaeologists and resource managers are starting to recognize the value of studying ancient cultures for examples of how resources have, and have not, been sustainably utilized in the past as a way of understanding current trends in environmental degradation. These studies do not provide sweeping generalizations about aboriginal resource use but, rather, identify the range of conditions under which sustainable harvests may be possible. The hypothesis of sustainable harvests must be tested using variables that can be measured equally well in ancient (e.g., archaeological) and modern contexts. These factors are carefully considered in this analysis of pinniped (seal and sea lion) remains from two archaeological sites on the eastern North Pacific (ENP) coast, where pinnipeds have been hunted for millennia. Reconstruction of the age composition, or harvest profile, of Callorhinus ursinus at the Ozette Village Site, Washington, shows that males and females of all ages were harvested, and supports the hypothesis that it was done so sustainably for over 500 years. After this period of apparent stability, C. ursinus abandoned local breeding colonies in the early historic period. In contrast, harvests of this species at the Moss Landing Hill Site, California, primarily targeted young of the year, and sub-adult and adult females. While this harvest is also inferred to have targeted a local breeding colony, C. ursinus appear to have been extirpated nearly 2000 years earlier at Moss Landing than at Ozette. The causes of these extirpations are not known, but the timing does not correspond well with known climatic changes, suggesting that subsistence, and perhaps commercial, hunting may have played a role. These examples underscore the need to recognize that patterns of resource use are highly variable – different cultures have had varying levels of effects on economically important species, and these effects have varied temporally, spatially, and taxonomically.

Natural History, Courtship, Feeding Behaviour and Parasites ofTheridion evexum(Araneae: Theridiidae)

Summary Theridion evexum constructs webs in the understory of wet middle-elevation forests in Costa Rica. The spiders construct retreats by curling a leaf and produce a mesh in front of the opening. Long, more or less vertical viscid lines extend from the mesh, and are attached to other leaves. The spiders feed on a large variety of prey (e.g. flies, beetles, earwigs, centipedes), indicating that both flying and walking arthropods are trapped in their webs. The wrapping threads have large viscid globules that rapidly disperse on the prey’s surface, forming a thin film. Adult males guard subadult females in their retreats, possibly waiting for them to moult and copulate. As part of courtship, the male places his pedipalps several times on the female’s mouthparts, then one pedipalp on her mouthparts and the other on her epigynum before insertion. Eggs were parasitised by Baeus (Scelionidae) and juveniles and subadults by Zatypota petronae (Ichneumonidae). Eggs were eaten by Argyrodes sp. (Theridiidae), and Solenopsis ants stole prey accumulated in the retreats and attacked spiderlings and older juveniles.

Space use, habitat selection and browsing effects of red deer in Sardinia

Sound ecological data are important for the conservation of the endangered Sardinian red deer, but mainly anecdotal information is available. Deer density in Mt. Arcosu WWF Reserve was 25–26 deer/100 ha. We radiotracked 8 hinds and 2 stags. Mean annual home range size was 36.5 ha (hinds) and 65.9 ha (stags). On the rut, adult females increased their home ranges by 25% and subadult females by 80%. At birthing, female home ranges reached a minimum. Small home ranges of our deer were probably related to the mild climate and dense evergreen vegetation, providing food and cover. Hinds always moved more than stags. Site fidelity was shown to areas rich in food and cover, except on the rut. In days with tourists, mean home range size significantly increased and deer selected wooded areas, whereas they preferred open terrain in days without tourists. A stronger response to disturbance occurred during the rut and in winter, when deer were less habituated to tourists. Maximum habitat selection occurred in spring and summer, when open areas were rarely used. A lethal impact on uncommon species, because of overbrowsing, was observed on 1.3% of plants. The overall impact on vegetation was negligible, despite the great deer density.

Success of Grizzly Bear Population Augmentation in Northwest Montana

Abstract: Augmentation of large carnivore populations can be a valuable management and recovery tool, but success of many programs has not been well documented. The Cabinet—Yaak grizzly bear (Ursus arctos) population was located in northwestern Montana and northern Idaho, USA, and was estimated at 30–40 individuals. The Cabinet Mountains portion of this area may be isolated from the remainder of the zone and was the site of a test of grizzly bear population augmentation. Experimental objectives included evaluating site fidelity, reproduction, and long‐term survival of the translocated bears. Four subadult females (2–6 yr old) were translocated from southeastern British Columbia, Canada, from 1990 to 1994. Three of 4 transplanted bears remained in the target area for ≥1 year and satisfied the short‐term goal for site fidelity. Recent genetic evidence gathered through hair‐snagging efforts has determined that at least one of the original transplanted animals has reproduced, thereby providing evidence of success for the long‐term goals of survival and reproduction.