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Hibernation provides a means of escaping the metabolic challenges associated with seasonality, yet the ability of mammals to prolong or reenter seasonal dormancy in response to extreme weather events is unclear. Here, we show that Arctic ground squirrels in northern Alaska exhibited sex-dependent plasticity in the physiology and phenology of hibernation in response to a series of late spring snowstorms in 2013 that resulted in the latest snowmelt on record. Females and nonreproductive males responded to the >1-month delay in snowmelt by extending heterothermy or reentering hibernation after several days of euthermy, leading to a >2-week delay in reproduction compared to surrounding years. In contrast, reproductive males neither extended nor reentered hibernation, likely because seasonal gonadal growth and development and subsequent testosterone release prevents a return to torpor. Our findings reveal intriguing differences in responses of males and females to climatic stressors, which can generate a phenological mismatch between the sexes.

In herbivores, survival and reproduction are influenced by quality and quantity of forage, and hence, diet and foraging behavior are the foundation of an herbivore's life history strategy. Given the importance of diet to most herbivores, it is imperative that we know the species of plants they prefer, especially for herbivorous species that are at risk for extinction. However, it is often difficult to identify the diet of small herbivores because: (a) They are difficult to observe, (b) collecting stomach contents requires sacrificing animals, and (c) microhistology requires accurately identifying taxa from partially digested plant fragments and likely overemphasizes less‐digestible taxa. The northern Idaho ground squirrel (Urocitellus brunneus) is federally threatened in the United States under the Endangered Species Act. We used DNA metabarcoding techniques to identify the diet of 188 squirrels at 11 study sites from fecal samples. We identified 42 families, 126 genera, and 120 species of plants in the squirrel's diet. Our use of three gene regions was beneficial because reliance on only one gene region (e.g., only trnL) would have caused us to miss >30% of the taxa in their diet. Northern Idaho ground squirrel diet differed between spring and summer, frequency of many plants in the diet differed from their frequency within their foraging areas (evidence of selective foraging), and several plant genera in their diet were associated with survival. Our results suggest that while these squirrels are generalists (they consume a wide variety of plant species), they are also selective and do not eat plants relative to availability. Consumption of particular genera such as Perideridia may be associated with higher overwinter survival. Diet and foraging behavior are the foundation of an herbivore's life history strategy and it is imperative that we know the species of plants they prefer. We used DNA metabarcoding techniques to noninvasively sample the threatened northern Idaho ground squirrel (Urocitellus brunneus) diet. We used three gene regions and found that diets differed on the genus level between season, availability, and survival was associated with particular plants.

Otospermophilus douglasii (Richardson, 1829), the Douglas ground squirrel, was first described as a species and then relegated to a subspecies of the California ground squirrel, O. beecheyi (Richardson, 1829). However, genetic data recently were interpreted as indicative of returning O. douglasii back to valid species status. This semi-fossorial, social species is brown with small white spots, a dark dorsal patch, and silvery shoulders. Occupying diverse habitats and elevations, this native species is an important prey species and is most abundant in grasslands and open woodlands. It forages primarily on seeds and vegetation but is also in conflict with humans as a crop pest and disease vector that damages infrastructure through creating elaborate burrow systems. Currently, the International Union for Conservation of Nature has not provided a conservation assessment for O. douglasii.

We evaluated the hypothesis that social play behavior influences the development of temperament in young animals, using docility as a measure of temperament. We observed the play behavior of juvenile Belding’s ground squirrels (Urocitellus beldingi) during the developmental period in which play primarily occurs and conducted behavioral tests measuring docility at the beginning and toward the end of the play interval. Tests involved handling squirrels and recording their responses. We observed a significant but weak association between body mass and docility at the beginning of the play period, suggesting that docility may vary with size or energetic variables. Docility decreased significantly among juveniles over the play interval, and rates of social play were reliable predictors of change in docility. Juveniles who played at higher rates tended to have greater decreases in docility over the play interval, suggesting that social play might refine temperament toward more active responses in U. beldingi. Rates of social play among juveniles were reliable predictors of their scores on docility tests as yearlings, suggesting that possible effects of juvenile play on docility may extend beyond the juvenile period. Among mothers of juveniles in the study, docility during gestation and lactation were reliable predictors of docility after emergence of young from the natal burrow. However, docility of mothers decreased significantly between gestation and emergence of young, suggesting that although squirrels have individual tendencies toward docility, the expression of these tendencies may be influenced by behavioral context.Significance statementThis study helps to elucidate ways in which juvenile social play influences the development of young animals. Various studies have suggested that juvenile play influences motor, social, and cognitive development. Here, we show an association between juvenile social play and development of temperament in Belding’s ground squirrels (Urocitellus beldingi). Juveniles who engaged in play at higher rates across the play interval had greater behavioral shifts from passive toward active responses. Refinements in temperament toward more proactive behavior might have benefits for young animals such as better preparing them to explore, investigate, and gather information about their social and physical environments as they venture away from their natal areas.

Many animals socialize in two or more major ecological contexts. In nature, these contexts often involve one situation in which space is more constrained (e.g. shared refuges, sleeping cliffs, nests, dens or burrows) and another situation in which animal movements are relatively free (e.g. in open spaces lacking architectural constraints). Although it is widely recognized that an individual's characteristics may shape its social life, the extent to which architecture constrains social decisions within and between habitats remains poorly understood. Here we developed a novel, automated-monitoring system to study the effects of personality, life-history stage and sex on the social network structure of a facultatively social mammal, the California ground squirrel (Otospermophilus beecheyi) in two distinct contexts: aboveground where space is relatively open and belowground where it is relatively constrained by burrow architecture. Aboveground networks reflected affiliative social interactions whereas belowground networks reflected burrow associations. Network structure in one context (belowground), along with preferential juvenile–adult associations, predicted structure in a second context (aboveground). Network positions of individuals were generally consistent across years (within contexts) and between ecological contexts (within years), suggesting that individual personalities and behavioural syndromes, respectively, contribute to the social network structure of these free-living mammals. Direct ties (strength) tended to be stronger in belowground networks whereas more indirect paths (betweenness centrality) flowed through individuals in aboveground networks. Belowground, females fostered significantly more indirect paths than did males. Our findings have important potential implications for disease and information transmission, offering new insights into the multiple factors contributing to social structures across ecological contexts. This article is part of the theme issue ‘Interdisciplinary approaches for uncovering the impacts of architecture on collective behaviour’.

Whether hibernation accelerates or suppresses autophagy is still unknown. In the current study, we examined changes in autophagy in oxidative soleus (SOL) muscle in summer active (SA), pre-hibernation (PRE), torpor (TOR), interbout arousal (IBA), and post-hibernation groups of Daurian ground squirrels (Spermophilus dauricus). Here, the SOL muscle showed no significant atrophy during hibernation in regard to muscle wet weight, fiber cross-sectional area, or MuRF1 protein level. Autophagy-related proteins beclin1 and Atg7 increased significantly, whereas LC3-II decreased significantly in the PRE group compared with the SA group. However, neither the expression nor activity of cathepsin L showed any differences between the SA and PRE groups. In addition, beclin1, LC3-II, and the LC3-II/LC3-I ratio increased, p62 decreased, LC3 puncta increased, p62 puncta decreased, and cathepsin L activity increased in the TOR group compared with the PRE group. In contrast, beclin1, LC3-II, and the LC3-II/LC3-I ratio decreased, p62 increased, LC3 puncta decreased, p62 puncta increased, and cathepsin L activity declined in the IBA group compared with the TOR group. Moreover, the phosphorylation of Akt (Ser473) and mTOR (Ser2448) changed significantly during hibernation and showed an inverse relationship with autophagy changes. In conclusion, autophagy proteins displayed periodic oscillation in the torpor-arousal cycle, which may be advantageous in maintaining SOL muscle mass during the entire hibernation period. Furthermore, the Akt-mTOR signaling was decreased in TOR and increased in IBA group in the SOL muscle of Daurian ground squirrels during hibernation.

Context Promoting grassland habitat networks within agricultural landscapes is essential for supporting biodiversity. However, the characteristics of these networks are often poorly documented, making it difficult to prioritize conservation strategies and effectively protect grassland-dependent species. Objectives We set to identify conservation priorities for (semi)natural grasslands by assessing habitat network characteristics based on a combination of monitoring data and scientific model output for European Ground Squirrel (EGS), a keystone grassland specialist, in agricultural settings of northern Serbia. Methods We used the spatially explicit model, LARCH, to determine the current habitat networks and available monitoring data on presence/absence and habitat suitability together with Circuitscape to better understand the characteristics of those networks. The combination of modeling results and monitoring data was used to prioritize conservation measures for each network to support a stable and viable EGS metapopulation. Results We identified 15 habitat networks. Our analysis showed that two of these need no interventions, but most of them need a mix of improving habitat quality and connections within and between the networks to support local populations and the metapopulation overall. Conclusions Results revealed areas in which spatial adaptation measures (e.g., grassland restoration and corridor development) should be deployed to accommodate the long-term survival of EGS. It might be considered to stop conservation efforts in some abandoned networks as the network characteristics are too poor, and resources should be used to improve habitat networks that are still occupied. Our findings may guide the conservation of (semi)natural grasslands and future sustainable land-use planning in intensively farmed landscapes.

Scavengers are subsidized by the remains of hunting worldwide. Although most studies focus on carcasses of large mammals, small mammals that have been shot likely provide a significant food subsidy as well, particularly in parts of the western United States. Millions of small mammals are estimated to be shot each year for damage control and recreation, many being left in the field. Despite this prevalence of carrion, and the potential for scavengers to ingest residual lead from bullet fragments, the fate of these carcasses is largely unknown. We deployed remote cameras to observe which scavengers consumed shot ground squirrels (Urocitellus spp.) and black-tailed prairie dogs (Cynomys ludovicianus) in 8 locations across Montana, USA. At least 5 species of mammals and 9 species of birds scavenged, including burrowing owls (Athene cunicularia). Scavengers fully consumed 66% of carcasses and partially consumed 9%. Carcasses lasted an average of 24.5 hours before the first scavenger arrived. Of carcasses that were scavenged, mammals ate 16% and birds ate 84%, with corvids and raptors consuming an equal number of carcasses. Common ravens (Corvus corax) and black-billed magpies (Pica hudsonia) visited the most carcasses and often arrived first. Scavengers consumed only 9% of the carcasses that were partially concealed by being inside a burrow. Overall, our results indicate that a diverse scavenger community consumes shot ground squirrels and black-tailed prairie dogs, and consequently, may be exposed to lead from bullet fragments.

Energy conservation associated with hibernation is maximized at the intersection of low body temperature (T b ), long torpor bouts, and few interbout arousals. In the arctic ground squirrel ( Urocitellus parryii ), energy conservation during hibernation is best achieved at ambient temperatures (T a ) around 0 °C; however, they spend the majority of hibernation at considerably lower T a . Because arctic ground squirrels switch to mixed fuel metabolism, including protein catabolism, at extreme low T a of hibernation, we sought to investigate how microbial urea-nitrogen recycling is used under different thermal conditions. Injecting squirrels with isotopically labeled urea ( 13 C/ 15 N) during hibernation at T a ’s of − 16 °C and 2 °C and while active and euthermic allowed us to assess the ureolytic activity of gut microbes and the amount of liberated nitrogen incorporated into tissues. We found greater incorporation of microbially-liberated nitrogen into tissues of hibernating squirrels. Although ureolytic activity appears higher in euthermic squirrels, liberated nitrogen likely makes up a smaller percentage of the available nitrogen pool in active, fed animals. Because non-lipid fuel is a limiting factor for torpor at lower T a in this species, we hypothesized there would be greater incorporation of liberated nitrogen in animals hibernating at − 16 °C. However, we found higher microbial-ureolytic activity and incorporation of microbially-liberated nitrogen, particularly in the liver, in squirrels hibernating at 2 °C. Likely this is because squirrels hibernating at 2 °C had higher T b and longer interbout arousals, a combination of factors creating more favorable conditions for gut microbes to thrive and maintain greater activity while giving the host more time to absorb microbial metabolites.

The thirteen-lined ground squirrel, Ictidomys tridecemlineatus, is a mammal capable of lowering its Tb to almost 0 °C while undergoing deep torpor bouts over the winter. To decrease its metabolic rate to such a drastic extent, the squirrel must undergo multiple physiological, biological, and molecular alterations including downregulation of almost all nonessential processes. Epigenetic regulation allows for a dynamic range of transient phenotypes, allowing the squirrel to downregulate energy-expensive and nonessential pathways during torpor. DNA methylation is a prominent form of epigenetic regulation; therefore, the DNA methyltransferase (DNMT) family of enzymes were studied by measuring expression and activity levels of the five major proteins during torpor bouts. Additionally, specific cytosine marks on genomic DNA were quantified to further elucidate DNA methylation during hibernation. A tissue-specific response was observed that highlighted variant degrees of DNA methylation and DNMT expression/activity, demonstrating that DNA methylation is a highly complex form of epigenetic regulation and likely one of many regulatory mechanisms that enables metabolic rate depression in response to torpor.