Geographic patterns in scatterhoarding behavior of eastern gray squirrels Sciurus carolinensis

Scatter-hoarding behavior in Siberian chipmunks (Tamias sibiricus): An examination of four hypotheses

Congeneric fox squirrels (Sciurus niger) and eastern gray squirrels (S. carolinensis) compete for resources within North American temperate forests. Both species exhibit regional variation in morphology and behavior—potentially due to differences in geography, community composition, or ecological pressures between forested regions. While many have studied these species in other forested regions of the United States, recent assessments of partitioning between these species in Central Hardwood forests remain scarce. We investigated spatial and temporal partitioning between squirrel species using photographic captures from camera traps at 2 scales (i.e., camera location and camera cluster) across a 16,058-km2 region of southern Illinois, United States, during January to April 2008 to 2010. We fitted single-season single-species and co-occurrence occupancy models to assess spatial partitioning at both scales and used kernel density analysis to assess temporal partitioning. We recorded 3,044 photographic captures of focal species (n = 918 fox squirrels and 2,126 eastern gray squirrels). Fox Squirrel occupancy was 0.26 ± 0.09 (SE) and 0.50 ± 0.17 at the camera location and camera cluster scales, respectively. Eastern Gray Squirrel occupancy was 0.47 ± 0.07 and 0.84 ± 0.23 at the camera location and camera cluster scales, respectively. Fox Squirrel occupancy increased with further distances to roads and had scale-dependent relationships to forest structure. Eastern Gray Squirrel occupancy increased with more hardwood basal area. Co-occurrence was influenced by distance to road at the camera location scale. We found a moderate level of activity overlap between species (Δ = 0.63, CI = 0.60 to 0.67); however, no evidence of temporal partitioning was observed. Habitat characteristics and spatial scale appear more influential in partitioning eastern gray and fox squirrels in Central Hardwood forests than peak activity.

The nutrition of wild animals affects their ability to survive, reproduce, and ultimately persist in unpredictable environments. Nutrition interacts with the life history of animals across different scales (Smiley, LaSharr, et al., 2022), from long-term and cross-generational effects that dictate phenotype and reproductive success (Michel et al., 2016), to influences of their current environment on survival (Parker et al., 2009). For large mammals, nutrition underpins much of what they do. Particularly in temperate environments with harsh conditions and severe limitation of resources for extended periods, animals rely heavily on energy stored as fat during winter when resources are scarce (Mautz, 1978; Parker et al., 2009). In seasonal environments, the pattern of fat accumulation and depletion is closely synchronized to their environment and availability of resources (Smiley, Wagler, et al., 2022). Nevertheless, to survive when severe environmental conditions result in an unanticipated but necessary depletion in fat reserves, animals that persist are faced with severe consequences for reproduction that can span years or even generations. The environmental, physiological, and nutritional state of a mother has a lifetime effect on her offspring (Bernardo, 1996), and for ungulates, the nutrition of the mother during gestation can have an important and often underappreciated effect on the lifetime phenotype, behavior, and success of her offspring (Michel et al., 2016). The link between maternal nutrition and offspring performance may have important consequences for how populations or species respond to changing environments. Research in captive settings has shown, even with animals that are closely related (i.e., have similar genetic makeups), maternal condition can have serious lifetime implications for an animal's offspring; mothers in poor condition give birth to sons that exhibit stunted growth compared with sons born to mothers in good condition (Monteith et al., 2009). Yet, identifying the role of maternal effects in wild animals can be difficult. It requires information on the nutritional legacy of a mother in combination with information on current environmental conditions (Benton et al., 2001). Garnering data necessary to disentangle the effects of current nutritional state, environment, and maternal effects requires repeated sampling of mothers and their offspring through time. Long-term, individual-based research is expensive, and logistically challenging, but can provide intricate data to test complex questions and theories. Through a long-term research project, we observed how the nutritional legacy of a harsh winter before an animal's birth potentially influenced the growth and development of a male mule deer (Odocoileus hemionus) born in the wild. As part of a research project that was focused on disentangling the mechanisms of population performance of mule deer, in December 2013 in Wyoming, USA, we captured 70 adult females and fitted them with GPS collars (ATS, Iridium and Vectronic Aerospace, Vertex Plus). Each spring and autumn following that initial capture until December 2021, we recaptured each individual. From 2015 to 2021, we captured newborns of collared females and fit them with expandable VHF or GPS collars (ATS and Vectronic Aerospace). We recaptured all surviving juveniles (both males and females) as adults each spring and autumn following their survival to adulthood. At each capture event for adults, we measured nutritional condition (i.e., percent body fat) and each spring we measured pregnancy and fetal rates of female deer via ultrasonography (see Aikens et al., 2021 for detailed methodology). At each autumn capture, we measured antler size of male deer using standard approaches including measurements of beam lengths, tine lengths, and antler circumferences (Monteith et al., 2014). This long-term, individual-based study has allowed us to begin to elucidate the cross-generational roles of nutrition in a wild population. Mule deer in this population inhabit the Salt and Wyoming Ranges of Wyoming, and each year migrate from low-elevation (~1800 m) winter ranges dominated by sagebrush steppe to high-elevation (~2300–27,500 m) summer ranges, comprised of tall forb, mixed-mountain shrub, aspen, and conifer communities. Peak parturition occurred in mid-June, after migration to summer ranges (Aikens et al., 2021). Overwinter survival was heavily dependent on stored fat accumulated over summer, and winter conditions could be harsh. To assess how winter weather influenced the nutrition of a female mule deer and the subsequent fitness of her offspring, we evaluated the condition of a collared deer (deer 096) and her collared, male offspring (deer MFFO) born after a severe winter and the next 4.5 years of his life. During the winter of 2016–2017, animals in this population encountered harsher conditions than they had experienced in nearly 30 years (snowfall that winter was 236.2 cm, the third greatest annual snowfall recorded for the state; Smiley, LaSharr, et al., 2022), with prolonged periods of subzero temperatures and more extreme snow conditions than average. Indeed, average body fat of animals when captured between 8 March and 10 March 2017 was 2.3% (average during normal winters 4.6%), and although deer 096 (7 years old) was in better shape than many of her counterparts with 4.1% body fat (Figure 1), this population faced an additional 2 months of extremely harsh winter conditions. Animals were pushed to their physiological limits and many succumbed to overwinter mortality; survival of collared females was 70% and survival of collared juveniles (<1 year old) was 0%. After this particularly harsh winter, survival of offspring born in the spring of 2017 was low: 29% of juvenile mule deer born that summer were stillborn or succumbed to malnutrition early (stillbirth/malnutrition ranged from 3% to 18% in other years), further exemplifying the nutritional stress experienced by female deer. On 1 June 2017, deer 096 gave birth to two offspring, one male (MFFO) and one female. Despite the harsh winter that depleted the majority of fat reserves of animals in this population, deer 096 carried two fetuses to term and was successful in her reproductive efforts, likely a product of her higher than average fat levels for the population in spring of 2017. Recruitment of two offspring was something that was not achieved by most mule deer during that summer. Indeed, MFFO was the only male from his cohort that we had collared as an adult; despite capture efforts of random, adult males on the landscape we have not captured a male born during the summer of 2017 on MFFO's winter range. Yet, despite deer 096's success in recruiting two offspring into the population, the legacy of the harsh winter that preceded his birth probably followed MFFO for the remainder of his life. Over the 4.5 years that followed his birth, we recaptured him at 2.5 and 3.5 years of age and measured his antlers and nutritional condition; additionally when he was harvested as a 4.5 year old, we measured his antlers following harvest. MFFO never achieved antler growth that was comparable with average males in his age class in the population (Figure 2). Indeed, each year his antlers appeared more similar to the age class below him than to his actual age class. Compared with other males in this population, MFFO's antlers were 30% smaller than the average 2.5 year old, 33% smaller than the average 3.5 year old, and 20% smaller than the average 4.5 year old in each respective year of his life (Figure 3). Moreover, the amount of fat he had in the autumn was often similar or higher (7% and 9.7% at 2.5 and 3.5 years of age, respectively), compared with other mature males (i.e., 6.4%). Even though his nutritional condition demonstrated that he had access to high-quality food, he was probably unable to achieve his full phenotypic potential. Although there is the potential that expression of genetic potential for antler size was below average for MFFO, we suspect his stunted trajectory of antler growth was in large part a response to his mother's condition when he was in utero and a consequence of a life-lasting maternal effect on growth. The effect of maternal condition on offspring phenotype has been investigated using an individual-based approach in captive settings (Michel et al., 2016; Monteith et al., 2009), and has been evaluated at the population level in wild systems (Monteith et al., 2017). Yet, an investigation of maternal condition on offspring using an individual-based approach has yet to be achieved in wild populations. Long-term, individual-based research provides the opportunity to better understand wild populations and the mechanisms that drive their trajectories. Although MFFO is only a single individual, his striking growth pattern and size may well be driven by the lasting, deleterious effects of the 2016–2017 winter. Moreover, the trajectory of MFFO's growth and the connection to extreme environmental conditions and maternal nutrition has provided a unique opportunity to communicate complex concepts of nutrition and maternal effects to nonscientific audiences. There is an inherent value in the connection to individual animals that accompanies individual-based, long-term research; it can provide tangible examples that allow scientists to demonstrate intricate ecological theory to the public in an understandable manner (Jakopak et al., 2019). Storytelling is an effective and engaging way to allow nonscientific audiences to process, understand, and retain scientific information (Joubert et al., 2019). The story of MFFO's life and growth provides an example of the potential lifetime consequences that a mother's nutrition might have for her offspring in a wild population, regardless of the short-term environments and resources they experience. As populations of large herbivores are exposed to increasingly extreme conditions, changes to nutrition might have unanticipated consequences for animal phenotypes. We thank B. Wagler, R. Smiley, E. Moberg, E. Monfort, and T. Faber for assistance with data collection on the Wyoming Range Mule Deer project during the summer of 2017. The Wyoming Range Mule Deer study was supported by the Wyoming Game and Fish Department, Wyoming Game and Fish Commission, Bureau of Land Management, Muley Fanatic Foundation (including Southwest, Kemmerer, Upper Green, and Blue Ridge Chapters), Boone and Crockett Club, Wyoming Wildlife and Natural Resources Trust, Knobloch Family Foundation, Wyoming Animal Damage Management Board, Wyoming Governor's Big Game License Coalition, Bowhunters of Wyoming, Wyoming Outfitters and Guides Association, Pope and Young Club, the United States Forest Service, and United States Fish and Wildlife Service. We thank the multiple landowners that kindly offered access to their property for this research. The authors declare no conflict of interest. Nutritional condition data (LaSharr, 2022) are available in Dryad at https://doi.org/10.5061/dryad.0rxwdbs3b.

An understanding of how species are affected by top‐down and bottom‐up processes in food webs, and how these forces interact with climatic conditions is crucial for how ecosystems should be managed. In Norway large carnivores are effectively removed from extensive areas to protect livestock, leaving human harvesting as the only significant top‐down force on ungulate populations. We examined the relative role of top‐down and bottom‐up processes for 58 semi‐domesticated reindeer populations in Norway subjected to contrasting climatic regimes over the period 1981–2005. Intensive herding and international agreement have resulted in a situation where some populations are unable to undertake seasonal migration to the interior to escape the unfavourable climatic conditions that rule the coastal region in the winter, a critical season for northern ungulates. We used this natural manipulation to contrast between populations with ‘poor’ and ‘good’ winter conditions. For populations with good winter conditions, average body size increased with harvesting, suggesting that some top‐down process was necessary to avoid food limitation. Time‐series analyses revealed that direct regulation of population size was only evident in populations subjected to intensive harvesting. The lack of direct regulation in populations subjected to low harvesting resulted in high vulnerability to harsh winter weather. The body size and climate vulnerability of populations with poor winter conditions was unaffected of harvesting, but average densities was positively related to overall vegetation productivity as indexed by satellite images (NDVI). Top‐down processes appeared to be necessary to dampen the effect of harsh winters in populations with generally good winter conditions. Conversely, populations subjected to generally poor winter conditions appeared to be more influenced by bottom‐up processes and buffered climatic perturbations by increasing body size.

Current environmental changes may affect the dynamics and viability of plant populations. This environmental sensitivity may differ between species of different ploidy level because polyploidization can influence life history traits. We compared the demography and climatic sensitivity of two closely related ferns: the tetraploid Polystichum aculeatum and one of its diploid parents, Polystichum setiferum. Matrix models were used to assess the effects of life history variation on population dynamics under varying winter conditions. We analyzed the contributions of all key aspects of the fern life cycle to population growth. Our study is the first to also include the gametophyte generation. Projected population growth rate (λ) was much higher for the tetraploid P. aculeatum (1.516) than for P. setiferum (1.071) under normal winter conditions. During a year with harsh winter conditions, population growth of P. aculeatum was strongly reduced. This finding contradicts our expectation that the winter-hardy fronds of this species would allow high survival of harsh winters. Differences in λ between species and between years with different winter conditions were mostly caused by variation in gametophyte-related recruitment rates, a finding that shows the importance of including gametophytes in fern demographic studies. Our results indicate that populations of closely related ferns can show large differences in population performance, mainly related to recruitment rates and frond phenology, and that these differences may depend greatly on climatic conditions. Our findings provide a first indication that (allo)polyploidization in ferns can have a significant effect on population dynamics.

Knowledge of the effect of harsh weather on the phenotypic traits of organisms is essential for understanding the environmental influence on phenotype evolution and holds implications for predicting how species respond to current climate change. For many birds, harsh weather in winter often imposes a strong selective effect on their survival, and only the individuals with certain phenotypes may survive. However, whether the selective effect on phenotype varies with winter weather conditions has been poorly investigated. Here, we explored the selective effect of winter weather on black-throated tit's (Aegithalos concinnus) morphological traits under winters with and without severe snowstorms. We found that for males, the sizes of their bills, heads and wings significantly affected their overwinter survival, but the effects varied with winter conditions. In relatively benign winters, males with smaller bill depths, smaller bill surface areas, and greater head lengths survived better; whereas, in winters with severe snowstorms, a reverse pattern was found. This phenomenon was likely driven by selection pressures from heat retention and foraging requirements, with their relative importance depending on winter conditions. Additionally, wing length was positively correlated with male survival and the relationship was stronger in harsher winters, which was probably due to longer wings' higher flight efficiency in adverse weather. By contrast, we found no correlation between morphological traits and survival in females. These results suggest a sex-specific and condition-dependent selective effect of environment on bird phenotypes, implying complicated interactions between different selection pressures and phenotype evolution.

Squirrels on North American college and university campuses have been the subject of much animated conversation in informal venues, but a systematic assessment of their distribution across this habitat type has not been undertaken until now. We collected reports of squirrel species’ presence and absence from faculty experts at 536 campuses in Canada and the continental United States, and found that squirrels are nearly ubiquitous on campuses (95% had at least one species, and 40% had three or more), but that only a select few species are common campus residents. Foremost among these is the eastern gray squirrel (Sciurus carolinensis—on 62% of surveyed campuses), followed by the eastern fox squirrel (Sciurus niger), eastern chipmunk (Tamias striatus), North American red squirrel (Tamiasciurus hudsonicus), and woodchuck (Marmota monax). Eastern gray and fox squirrels partition campuses with one another, both in their shared native/core range and on the West Coast. While these invasive eastern species are present on campuses on the West Coast, notably, contingency analysis did not provide evidence that they are the primary factor discouraging western gray squirrels (Sciurus griseus) from using these habitats. The inventory and analyses presented here can provide a basis for longitudinal studies both within and across campuses and may be productively combined with initiatives that involve students in research.

Winter bikesharing in US: User willingness, and operator’s challenges and best practices

Options for the construction of oil loading terminals are being considered. Special attention is paid to the use of single-point berths, which are widely used in world practice. The vast majority of such terminals use floating hoses, which are connected by their tail through flanges to standard manifolds located in the central part of the tanker hull (conventional loading). In winter conditions, such a scheme of cargo operations is subject to serious risks. To avoid it, Russian ports in the Arctic and the Far East use single-point tower-type berths with an outboard shroud, which is mounted on the bow loading system without touching the water. After bans were imposed on the use of a tanker fleet with a bow loading system, some operators of mooring systems faced the question of year-round use of conventional tanker loading using floating hoses. The results of an analysis of the risks associated with the use of floating hoses in winter conditions in the presence of ice in relation to existing single-point oil shipment systems are presented. The most dangerous situations are considered to be the impact of drifting ice on a floating hose during loading, as well as the relative movement of an ice mass with a hose frozen in it between cargo operations, which is quite a likely situation in a harsh winter. As the main principle of minimizing risks in prospective and existing terminals, it is proposed to avoid direct contact of the hose line with the water surface and with ice, changing its residual buoyancy to near-neutral values.

No abstract available

Species that live in ecosystems with extremely different seasonal conditions must balance the constraints of each season to survive. Alpine species that do not migrate seasonally are especially adept at balancing the constraints created by short growing seasons and long, harsh winters. We investigated the habitat characteristics of hoary marmots in western Montana to provide a better understanding about habitat selection at the southern extent of this species’ distribution. Hoary marmots are an alpine obligate of special concern in western Montana; given that climate change is impacting alpine ecosystems at a rapid rate, this species may be especially vulnerable at the southern edge of their range. We conducted occupancy surveys in three study areas along a latitudinal gradient in 2014 and 2015 to assess the importance of specific habitat characteristics to their presence on the landscape. Slope, aspect, and presence of shrubs were all important habitat characteristics. Marmots preferred shallow slopes and southern aspects, similar to findings from other studies on hoary marmots and other marmot species. Our results provide evidence that marmots may strike a balance between the environmental conditions they require during summer and winter. Shallow slopes typically accumulate deeper snow in winter that provide the best insulating snowpack. However, a preference for southern aspects allows for more snow‐free areas in spring, providing a slightly longer growing season than northern aspects. Hoary marmots may be selecting areas with shrubs because shrubs can accumulate deeper snow and the additional insulation can increase subnivian temperatures. Other studies suggest that marmot survival is influenced by snowpack, indicating that marmot distribution may be more closely tied to winter conditions rather than summer conditions. This highlights the difficulty of working on marmots and other alpine obligates, as most studies occur only during the short growing season. Given the current and projected increases in temperature and reduction in snowpack in Montana, areas that provide the winter conditions hoary marmots require may become more limited. Effectively conserving, monitoring, and managing alpine obligates under an uncertain climate future will require a closer look at how winter conditions drive habitat selection and distributions on the landscape.

The eastern gray squirrel (Sciurus carolinensis Gmelin) is a widely distributed rodent in North America, including introduced populations in western regions. Despite being widespread in urban and suburban ecosystems, their role as reservoirs for tick-borne pathogens has been understudied compared to other wildlife hosts. This study investigates the prevalence of ectoparasites and tick-borne pathogens in eastern gray squirrels across suburban habitats in Centre County, Pennsylvania, United States. Over 2 yr, squirrels were trapped across 5 sites and examined for ectoparasites. Ticks were the most common ectoparasites identified, followed by lice, fleas, and mites (in order of prevalence). Ixodes scapularis Say was the only tick species identified. The head, particularly the ears, was the most frequently infested body region. In addition to ectoparasite surveillance, we assessed the presence of tick-borne pathogens in squirrels and pathogens in ticks. Squirrels were RNA-positive for Borrelia burgdorferi ([Johnson, Schmid, Hyde, Steigerwalt & Brenner]), Anaplasma phagocytophilum (Foggie, 1949), Borrelia miyamotoi (Franca, 1910) Fukunaga, Babesia microti, and Rickettsia rickettsii (Wolbach, 1919). ELISA screened 61 serum samples collected from individual squirrels for antibodies to the Borrelia burgdorferi VlsE and Anaplasma P44 proteins. Sixty-two and 17% were positive for antibodies to VlsE and P44, respectively, indicating past or current infection. The data presented collectively contribute to our better understanding of pathogen exposure in eastern gray squirrels. The results highlight the potential role of the eastern gray squirrel in vector ecology and the epidemiology of tick-borne diseases. Enhanced surveillance efforts in peridomestic areas are warranted and may mitigate zoonotic risks to humans and domestic animals.

The Painted Bunting: A Songbird Facing Multiple Threats Charles E. Konrad The Painted Bunting is unquestionably the most colorful songbird in the southern United States (cover photo, Figure 1). The male exhibits dazzling splashes of blue, green, yellow, and red plumage, and the reserved female possesses a solid coat of bright green, which blends in with the brush and trees where the nest is located. Because of its limited geographical range and stealthy nature, relatively few birders have experienced the delight of seeing this bird, and its dramatically declining population (Dybas 2018) has further reduced the chances of spotting it. Click for larger view View full resolution Figure 1. Painted Bunting taken at Huntington Beach State Park in South Carolina on May 16, 2022. [End Page 293] The Painted Bunting is categorized into two subspecies that are nearly identical in appearance but display distinct geographical distributions separated by a distance on the order of 500 km (Yirka et al. 2021). The eastern subspecies, Passerina ciris, breeds in a region that stretches from coastal North Carolina to northern Florida and includes an inland area in southern South Carolina and southeastern Georgia. The western subspecies, Passerina pallidior, breeds in a region extending from coastal Louisiana and Texas northward to southeastern Kansas and southern Missouri (Yirka et al. 2021). During the fall, the eastern population migrates southward to southern Florida and portions of the Bahamas and Cuba, while the western population migrates to portions of coastal Mexico and Central America. Given their geographic separation, these two populations no longer interact or breed, suggesting that the Painted Bunting will eventually divide into two different bird species (Dybas 2018). Within its breeding region, the Painted Bunting is typically present in bushy areas and woodland edges, often staying hidden within the dense cover of the vegetation. The males may be spotted by looking in the direction of their warbling songs during the breeding season. They often appear on an exposed perch higher up in the brush or trees. While the male sings out to announce its territory, the female typically remains hidden in the brush near the nest. In suitable habitats, both the male and female may be seen frequenting bird feeders. There has been a concerning decline in the number of Painted Buntings over the last fifty-plus years. According to the Breeding Bird Survey, the bird’s combined eastern and western populations have declined about 55 percent over the last thirty years (Dybas 2018). Springborn and Meyers (2005) report that the estimated number of individuals in the eastern population, Passerina ciris, decreased by about 75 percent between 1966 and 1996. Since 1996, this population has become so sparse in places that it is difficult to get a handle on the population trends across the southeastern US (Meyers 2011). Concern for the decline in the eastern and western populations of the bird species prompted the U.S. Fish and Wildlife Service and Partners in Flight (Springborn and Meyers 2005) to identify the Painted Bunting as a “species of concern” and a “near threatened” species. Several factors have been tied to the decline in Painted Bunting populations. Habitat loss in the summer breeding areas is unquestionably a major factor in the rapid reduction of the eastern population (Meyers 2011, Springborn and Meyers 2005). Painted Buntings are most common in dense marine shrubs, particularly live oak, which occur along the coast, largely on the barrier and sea islands from the Carolinas southward to Georgia and northern Florida (Meyers 2011, Dybas 2018). Many of these islands have seen rapid residential and commercial development over the last several decades, and this has greatly diminished the acreage of the Painted Bunting’s breeding habitat. In addition, many of the individuals in this eastern population winter in South Florida, which has seen a similar pattern of development and consequent habitat loss. Also, the reduction in riparian habitats near the southern US and Mexican coastlines, which are used during migration by the western population, have further contributed to the population decline (Lowther et al. 1999, Sykes and Holzman 2005). Given its extraordinary colors and beauty, the Painted Bunting has unfortunately been trapped in portions of its wintering grounds and sold as a...

We used the four-striped field mouse, Rhabdomys pumilio (Sparrmann, 1784), to test the hypothesis that reproduction in a small, short-lived mammal will be opportunistic, characterized by temporal and spatial variation in the timing of events, and only be inhibited under harsh and predictable winter conditions. Field mice were trapped for three years in two regions of the Eastern Cape Province of South Africa, one that experienced a predictable and harsh winter (Mountain Zebra National Park; MZNP) and the other which experienced a milder winter (Thomas Baines Nature Reserve; TBNR). There was no winter inhibition of reproduction at TBNR, while at MZNP female reproductive activity was inhibited but males continued to produce spermatozoa in winter. We interpret this flexibility in the timing of reproduction as supporting an opportunistic reproductive strategy which may be an adaptation to the seasonal and often unpredictable climate of the region.

We used the four-striped field mouse, Rhabdomys pumilio (Sparrmann, 1784), to test the hypothesis that reproduction in a small, short-lived mammal will be opportunistic, characterized by temporal and spatial variation in the timing of events, and only be inhibited under harsh and predictable winter conditions. Field mice were trapped for three years in two regions of the Eastern Cape Province of South Africa, one that experienced a predictable and harsh winter (Mountain Zebra National Park; MZNP) and the other which experienced a milder winter (Thomas Baines Nature Reserve; TBNR). There was no winter inhibition of reproduction at TBNR, while at MZNP female reproductive activity was inhibited but males continued to produce spermatozoa in winter. We interpret this flexibility in the timing of reproduction as supporting an opportunistic reproductive strategy which may be an adaptation to the seasonal and often unpredictable climate of the region.