Browsing by Author "Creel, Nancy M."
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Item Hunting on a hot day: effects of temperature on interactions between African wild dogs and their prey(2016-11) Creel, Scott; Creel, Nancy M.; Creel, Andrea M; Creel, BridgetAs global temperatures increase, interactions between species are affected by changes in distribution, abundance and phenology, but also by changes in behavior. The heat dissipation limitation hypothesis suggests that the ability to dissipate heat commonly limits the activity of endotherms, a problem that should be particularly acute for cursorial predators and their prey in equatorial ecosystems. Allometric relationships suggest that heat dissipation should be a stronger constraint for larger species, so that (smaller) predators should be less affected than (larger) prey. We used data from 266 complete days of direct observation of African wild dogs (Lycaon pictus) in five packs over a period of 2 yr to test how deviations of temperature from that expected for the time of day affected eight measures of hunting effort and success. We found that higher temperatures disadvantaged the prey of wild dogs more than the dogs themselves, with increased hunting success and shorter pursuits on warmer days. Broadly, our results demonstrate that effects of temperature on behavior can alter interactions between species, exacerbating or offsetting the direct effects of climate change.Item Opposing effects of group size on reproduction and survival(2015-07) Creel, Scott; Creel, Nancy M.For cooperative breeders, we hypothesize that the effects of group size on reproduction and survival might run in opposition if the benefits of grouping cannot be shared without cost. We tested this hypothesis by examining relationships between group size, survival, and reproduction in African wild dogs (Lycaon pictus), cooperative hunters with highly cohesive packs within which reproduction is monopolized by the dominant male and female. The production and survival of pups are known to increase with increasing pack size, but the effect of pack size on adult survival has not been examined previously. Data from 366 individuals over a period of 6 years showed that the survival of adults decreased with increasing pack size, with a 25% difference between the largest and smallest packs after controlling for the effects of age, sex, social status, year of study, and pack identity. Several tests confirmed that undetected dispersal is unlikely to have produced this pattern. These results suggest that cooperative breeding in wild dogs cannot be fully explained by mutual direct benefit, thus reinforcing the prior inference that kin selection plays an important role in the evolution of their cooperation. The results also weaken support for the hypothesis that wild dogs are extinction prone due to group-level Allee effects. More broadly, the relationship of effects of group size on survival and reproduction might be predicted by considering whether cooperation yields benefits that accrue to all group members (e.g., through cooperative vigilance) or benefits that must be apportioned to individuals (e.g., through cooperative hunting).