Time as a constraint on the distribution of feral goats at high latitudes

Abstract

We use data on feral goats on the Isle of Rum to explore the hypothesis that time is a major constraint on the latitudinal and altitudinal distribution of this species. Daylength and temperature were the principal factors influencing the main time budget elements (feeding, moving and resting). Because the goats do not feed at night due to low ambient temperatures, they faced particular problems during winter when daylengths were at their shortest. A mean monthly windchill‐adjusted temperature of 5°C appeared to be a critical threshold in terms of the animals’ ability to survive on Rum. We used these data to model the animals’ time budgets at different latitudes and altitudes. We show that winter daylength would be shorter than the required feeding time north of about 60° latitude, with a narrowing altitudinal cone approaching sea level at this latitude. Biogeographic evidence confirms that feral goat populations are not self‐sustaining north of this latitude.

Demographic effects of artificial nighttime lighting on animal populations

“…Because the failure to meet nutritional requirements will lead to starvation and death, fulfilling feeding time is assumed to take precedence over the other categories. Indeed, it is well established that the distribution and abundance of many species are constrained by the amount of time available for foraging (e.g., Sanz et al 2000;Dunbar et al 2009;Carrascal et al 2012;Zárybnická et al 2012;Dunbar and Shi 2013). This is particularly the case when temperatures are low and thus metabolic demands are high, when individual resource units are nutritionally poor, and when foraging at particular times carries high risks of predation.…”

Interactions with humans impose time constraints on urban-dwelling rhesus macaques (Macaca mulatta)

“…Resting time, for instance, is important for digestion, energy recovery, and thermoregulation (Herbers, 1981;Korstjens et al, 2010;McFarland et al, 2014), while social interactions (at least for group-living animals) play an important role in animals' ability to cope with environmental and social stressors (Silk et al, 2003;Frère et al, 2010;Formica et al, 2012). This can explain why time constraints tend to affect animal's group size (Chapman et al, 1995;Korstjens et al, 2006;Pollard & Blumstein, 2008), geographic distribution (Dunbar, 1992;Korstjens et al, 2010Korstjens et al, , 2018Dunbar & Shi, 2013), reproductive success (Siikamäki, 1998), mate choice (Backwell & Passmore, 1996), and, ultimately, survival (Dunbar et al, 2009). Consequently, animals are expected to make careful decisions when deciding how much time to devote to each activity in order to increase their chances of survival (Dunbar et al, 2009).…”

Environment and time as constraints on the biogeographical distribution of gibbons

“…One is that studies vary in the definitions they use for individual behavior categories; a second is that methods of collecting time budget data vary, both in intensity (e.g., some researchers use group scans, others focal individual sampling) and in coverage (the hours of daylight may not be sampled evenly). While these are certainly issues, past experience developing time budget models suggests that the impact of these methodological issues is at best modest (see Dunbar & Shi, ). More importantly, the main consequence of variations in definition and procedure is that they increase the error variance in parameter estimates; increased error variance will simply make it harder to obtain significant results, and will therefore bias the statistical analysis in favor of the null hypothesis (i.e., no relationship).…”

“…As in our previous models for African primates, the standard deviation of mean monthly temperature (TmoSD) is our main index of seasonality. This also allows us to include any effects due to the fact that, in some contexts, certain times of the year when resource availability is poor or climate especially challenging may impose limits on what animals can do (see, e.g., Dunbar & Shi, ).…”

“…Time budget models have been published for a number of terrestrial (gelada: Dunbar, ; baboons: Bettridge, Lehmann, & Dunbar ; Dunbar, ; African great apes: Lehmann, Korstjens, & Dunbar, , ) and arboreal (spider monkeys: Korstjens, Verhoeckx, & Dunbar, ; colobins: Korstjens & Dunbar, ; vervets: Willems & Hill, ; forest guenons: Korstjens, Lehmann, & Dunbar, ; orangutans: Carne, Semple, & Lehmann, ) primates, as well as one ungulate (feral goats: Dunbar & Shi, ).…”