Daily activity budgets reflect how animals balance internal physiological demands with external environmental pressures. We analyzed 14 037 camera‐trap records from 12 mammal species in the Venezuelan Llanos to evaluate the effects of foraging strategy (faunivore versus herbivore), season, and body mass on daily activity duration, to describe diel activity patterns, and to examine temporal overlap among species. Faunivores were active for nearly twice as long as herbivores (mean 12.1 versus 7.2 hours day −1 ), and trophic guild was the only significant predictor of daily activity duration. Activity duration did not differ significantly between wet and dry season at the community level, and body mass showed no significant effect once trophic guild was accounted for. Faunivores were primarily nocturnal, while most herbivores were diurnal. Although season had no general effect, some herbivores showed marked seasonal differences: eastern cottontail rabbit and white‐tailed deer were more active in the wet season, whereas capybara was more active in the dry season. Jaguar and puma showed very high temporal overlap, providing no evidence of temporal segregation between these two large felids, and overlap between large carnivores and their principal prey was only moderate. These results identify trophic guild as the strongest predictor of daily activity duration in this mammal assemblage and suggest that seasonal responses are species‐specific rather than general across herbivores.
Prairie dogs ( Cynomys spp.) are an important component of grassland ecosystems of North America where they can alter vegetation composition/structure and physical attributes of grassland habitats through their feeding and burrowing behavior. Impacts of prairie dog presence on many wildlife and plant taxa have been widely studied but research on prairie dog interactions with arthropods has been much scarcer. Due to the importance of many arthropods supplying various ecosystem services (e.g. pollination, pest control, etc.), an understanding of how prairie dogs potentially alter arthropod composition is warranted. Here we conducted a review of prairie dog interactions with arthropods compiling data from 50 sources, where we highlight three main relationships with arthropods: 1) arthropods living within prairie dog burrows, 2) arthropod consumption by prairie dogs, and 3) impacts on arthropod communities via habitat modifications by prairie dog feeding and construction of burrows. Most research connecting prairie dogs and arthropods was completed on the black‐tailed prairie dog Cynomys ludovicianus (68% of all sources), with very few studies conducted on the Utah and Mexican prairie dogs (6% of all studies). Prairie dogs do consume some arthropods and greatly impact various arthropod taxa within grassland ecosystems. Additionally, many arthropods use prairie dog burrow systems for shelter or permanent homes but these arthropods were infrequently studied. Overall, prairie dogs have potential to increase regional diversity (beta diversity) of arthropods by creating heterogeneity within the prairie landscape but more research is needed to elucidate how arthropod groups respond to habitat alterations caused by prairie dogs.
Many clinical signs of chronic wasting disease (CWD) in white‐tailed deer Odocoileus virginianus are consistent with those of chronic stress including hyperexcitability, head tremors, teeth grinding, pacing, excessive salivation, drinking, and urination. Deer with CWD‐positive (CWD+) status are more likely to exhibit poor body condition and to die, and clinical signs may be exacerbated by chronic stress. Chronic stress may inhibit the ability to fight secondary infections. Therefore, it is important to evaluate hormones linked to stress, such as cortisol, and their relationship with CWD status. We tested whether cortisol concentrations were associated with CWD status by quantifying cortisol in hair from hunter‐harvested deer. We supplemented this analysis with a small sample size (n = 9) of serum from captured deer where CWD status was known within 30 days of capture due to mortality. Cortisol in hair is representative of long‐term cortisol concentrations. In contrast, serum cortisol represents stress during capture and is highly variable by individual. In hair from hunter‐harvested deer, cortisol concentrations were significantly higher in CWD+ animals (p = 0.033). Cortisol concentrations in the hair of CWD+ deer were 1.3 pg mg −1 hair, (SE = 0.24) and for CWD non‐detect (ND) were 0.79 pg mg −1 , (SE = 0.09). Despite small sample sizes, serum cortisol was still on average higher in CWD+ (X‐= 5.9 μg dl −1 , SE = 1.6) compared to CWD ND deer (X‐= 2.9 μg dl −1 , SE = 1.3), though this relationship was not significant (p = 0.183). Combining these independent tests, there was significant evidence that cortisol concentrations differed between CWD+ and CWD ND animals (Fisher's method: p = 0.031). There is mounting biological evidence that this observed association is directionally causal – CWD likely causes elevated cortisol and not vice versa. These results indicate that chronic stress may facilitate the adverse effects of CWD and make deer more susceptible to other sources of mortality.
European hamster populations are rapidly declining all over their distribution area. One of the suggested reasons is a strong and ongoing decrease in the reproductive output of about 77% since the nineteen twenties. The cause of this decline is, however, unknown. To find out why the reproduction rate has decreased, precise information on the phenology of reproduction and litter‐sizes is necessary. In this study we show that recordings of body temperature (T b ) and activity of European hamster females provide accurate information on the reproductive phenology as well as individual health and death. In contrast to non‐gravid females, thermograms and actograms of gestating and lactating females clearly show arrhythmic patterns. Parturition is indicated by a profound hypothermia. The duration of the decline part correlates with the litter‐size. Thus, the timing and number of litters as well as the litter‐size can be precisely determined in T b recordings. Moreover, after parturition females show rhythmic patterns of activity and T b only after separation from the pups, no matter at which postnatal day that happens, allowing conclusions whether at least one pup could be raised to independence. In a pilot study we recorded T b in wild European hamster females in a Dutch population which is regularly restocked by captive bred animals. These data support the hypotheses that European hamsters currently reproduce too less and too late in order to keep the population stable. A helpful side‐effect of activity and temperature recordings is that they allow to determine the exact date and time of death of transmitter‐tagged individuals and thus conclusions about the reason. With the exception of the sensor implantation, monitoring T b is a non‐invasive method to study the life history of small mammals. Monitoring reproduction of small mammals might be a helpful tool to understand the massive global decline of species.
