Daily Activity and Nest Occupation Patterns of Fox Squirrels (Sciurus niger) throughout the Year

Abstract

The authors investigated the general activity and nest occupation patterns of fox squirrels in a natural setting using temperature-sensitive data loggers that measure activity as changes in the microenvironment of the animal. Data were obtained from 25 distinct preparations, upon 14 unique squirrels, totaling 1385 recording days. The animals were clearly diurnal, with a predominantly unimodal activity pattern, although individual squirrels occasionally exhibited bimodal patterns, particularly in the spring and summer. Even during the short days of winter (9 hours of light), the squirrels typically left the nest after dawn and returned before dusk, spending only about 7 hours out of the nest each day. Although the duration of the daily active phase did not change with the seasons, the squirrels exited the nest earlier in the day when the days became longer in the summer and exited the nest later in the day when the days became shorter in the winter, thus tracking dawn along the seasons. During the few hours spent outside the nest each day, fox squirrels seemed to spend most of the time sitting or lying. These findings suggest that fox squirrels may have adopted a slow life history strategy that involves long periods of rest on trees and short periods of ground activity each day.

Individual Daily and Seasonal Activity Patterns in Fox Squirrels (Sciurus niger) Quantified by Temperature-Sensitive Data Loggers

“…The monitoring of collar temperature (T c ) is particularly suited to provide an index of location (in-nest vs. out-of-nest), as the temperature of the collar quickly rises to core temperature levels after the animals enter their thermally insulated nests and drops rapidly when the animals leave their nests (Lamb, 1995;Kanda et al, 2005;Lazerte and Kramer, 2011;Murray and Smith, 2012;Wassmer and Refinetti, 2016). These assumptions were confirmed by aligning T c -records with behavioral logs (Wassmer and Refinetti, 2016) including nest entries. A recent study using a very similar setup with a large population of North American red squirrels (Tamiasciurus hudsonicus) confirmed the paradigm with about 700 observations of nest exits and entries (Studd et al, 2016).…”

“…Research on both aspects of activity is therefore essential to understand the biology of animal species. Locomotor activity has been shown to follow a reproducible daily pattern in numerous animal species, including tree squirrels (Tester, 1978;Adams, 1984;Koprowski and Corse, 2005;Wassmer and Refinetti, 2016). More than half a century ago, Aschoff (1966) observed that many, if not most, studies of locomotor activity had evinced a bimodal pattern with increased activity at dawn and dusk rather than a consolidated bout during the day or a consolidated bout during the night.…”

“…However, most published data on tree squirrel species have reported average activity patterns for the observed group of animals or population and provided no indications about the variability of these activity patterns in individual animals (Hicks, 1949;Thompson, 1977;Wauters and Dhondt, 1987;Jodice and Humphrey, 1992;Wauters et al, 1992;Bordignon and Monteiro-Filho, 2000;Johnson et al, 2003;Koprowski and Corse, 2005;Ditgen et al, 2007). Only four studies so far have provided data on individual animals in tree squirrels (Zwahlen, 1975;Adams, 1984;Wassmer and Refinetti, 2016;Anders et al, 2017).…”

Behavioral classification of low‐frequency acceleration and temperature data from a free‐ranging small mammal

“…When attached externally to an animal, the temperature recorded is often intermediate between body temperature and the ambient temperature of the environment immediately surrounding the individual (Osgodd & Weigl, 1972;Studd, Boutin, McAdam, & Humphries, 2016;Tremblay, Cherel, Oremus, Tveraa, & Chastel, 2003). Most pertinent here, collar temperature likely offers useful information about behavioral state, as it tends to more closely approximate the body temperature of inactive animals confined in small spaces (e.g., thermal refuges) and to more closely approximate the air temperature experienced by active animals fully exposed to ambient conditions (Körtner & Geiser, 2000;Messier, Taylor, & Ramsay, 1994;Murray & Smith, 2012;Olson et al, 2017;Wassmer & Refinetti, 2016). However, depending on the ecology of the species and which of these two temperatures vary more, collar temperature can be used to monitor thermal exposure (Osgodd & Weigl, 1972;Kanda, Fuller, & Friedland, 2009) or heterothermic fluctuations indicative of torpor expression or hibernation (Lazerte & Kramer, 2016).…”

“…However, depending on the ecology of the species and which of these two temperatures vary more, collar temperature can be used to monitor thermal exposure (Osgodd & Weigl, 1972;Kanda, Fuller, & Friedland, 2009) or heterothermic fluctuations indicative of torpor expression or hibernation (Lazerte & Kramer, 2016). Most pertinent here, collar temperature likely offers useful information about behavioral state, as it tends to more closely approximate the body temperature of inactive animals confined in small spaces (e.g., thermal refuges) and to more closely approximate the air temperature experienced by active animals fully exposed to ambient conditions (Körtner & Geiser, 2000;Messier, Taylor, & Ramsay, 1994;Murray & Smith, 2012;Olson et al, 2017;Wassmer & Refinetti, 2016).…”