On the scaling of activity in tropical forest mammals

Abstract

Activity range – the amount of time spent active per day – is a fundamental aspect contributing to the optimization process by which animals achieve energetic balance. Based on their size and the nature of their diet, theoretical expectations are that larger carnivores need more time active to fulfil their energetic needs than do smaller ones and also more time active than similar‐sized non‐carnivores. Despite the relationship between daily activity, individual range and energy acquisition, large‐scale relationships between activity range and body mass among wild mammals have never been properly addressed. This study aimed to understand the scaling of activity range with body mass, while controlling for phylogeny and diet. We built simple empirical predictions for the scaling of activity range with body mass for mammals of different trophic guilds and used a phylogenetically controlled mixed model to test these predictions using activity records of 249 mammal populations (128 species) in 19 tropical forests (in 15 countries) obtained using camera traps. Our scaling model predicted a steeper scaling of activity range in carnivores (0.21) with higher levels of activity (higher intercept), and near‐zero scaling in herbivores (0.04). Empirical data showed that activity ranges scaled positively with body mass for carnivores (0.061), which also had higher intercept value, but not for herbivores, omnivores and insectivores, in general, corresponding with the predictions. Despite the many factors that shape animal activity at local scales, we found a general pattern showing that large carnivores need more time active in a day to meet their energetic demands.

Camera‐trap data do not indicate scaling of diel activity and cathemerality with body mass in an East African mammal assemblage

“…Based on this systematic year-long camera-trap study, we found little support for diel activity levels to scale significantly and positively with body mass, or to differ between ruminants and nonruminants, or between herbivores and faunivores. For herbivores, the absence of a body mass scaling resembles the recent finding of Cid et al (2020).…”

“…In these species, terrestrial camera-trap placement may not represent their entire habitat niche and may thus result in biased activity patterns. In addition, our activity analyses are based on the sampled population of a species and did not differentiate between individual-level or sex-specific diel activity patterns, which F I G U R E 3 Relationship of activity levels and body mass from this study as compared to data obtained from 249 populations of terrestrial mammals in the tropics (Cid et al, 2020), distinguished as carnivores, herbivores, insectivores, and omnivores. Note the general overlap of data, that a scaling in herbivores may depend critically on including species smaller than available in the present study, and that the scaling in carnivores may depend critically on whether invertebrate and vertebrate prey are considered different trophic niches or not.…”

“…Gray-shaded areas represent night time, defined by the average time of sunrise and sunset during the study period ("catchability"), and quality of food are particularly variable in faunivores (Carbone et al, 2007). Comparative studies are further complicated by the fact that sometimes, invertebrate feeding is included in the category of "carnivory" (Carbone et al, 1999), and sometimes insectivory and carnivory are clearly distinguished (Cid et al, 2020).…”

Diurnal timing of nonmigratory movement by birds: the importance of foraging spatial scales

“…This is consistent with other findings concerning foraging space use: large‐bodied birds, which tend to feed on high‐quality resources and forage over large spatial scales (Schoener 1968), travel farther in homogeneous environments than heterogeneous environments (Tucker et al 2019). Among mammals, trophic level is correlated with home range size (Jetz et al 2004), which is positively correlated with activity levels (Cid et al 2020), suggesting a positive relationship between space use and activity levels over large scales.…”

“…These interact when animals forage, as they need to traverse the landscape according to their movement capacities to locate resources distributed non‐randomly in the environment (Suryan et al 2008). To maximize energetic gains from foraging, the timing of an animal's foraging movements is expected to correspond to either the temporal availability of its resources (Rydell et al 1996, Lang et al 2018) or the quantity and quality of resources required (Jetz et al 2004, Ramesh et al 2015, Cid et al 2020). Alternatively, animals can reduce their energy expenditure by timing their foraging activity when their movements are most energetically efficient (Chapman et al 2011, Shepard et al 2013) via behavioral thermoregulation (Matern et al 2000) and passive movement (Krupczynski and Schuster 2008).…”