Northeastern Naturalist Vol. 25, No. 3 M.L. Nelson and M. Sagot 2018 383 2018 NORTHEASTERN NATURALIST 25(3):383–390 Effects of Temperature and Day Length on Daily Movements and Home Range of Glaucomys volans (Southern Flying Squirrel) in the Northeastern United States Miranda L. Nelson1 and Maria Sagot1,* Abstract - To maximize energy gained and minimize energy expended, animals should forage in a manner that gives them the largest benefit at the lowest cost. Species living in seasonal environments in the northeastern US, such as the Glaucomys volans (Southern Flying Squirrel), need to overcome high energetic demands associated with thermoregulation and food availability. In this study, we measured nightly travelled distance and home range of Southern Flying Squirrel to understand how they adapt to changes in temperature and day length. Our results showed that Southern Flying Squirrel travelled longer distances and expanded their home range in warmer temperatures and longer day-lengths. Our study contributes to our understanding of how animals adapt to constantly changing environmental conditions in the northeastern United States. Introduction Foraging is an essential part of life for every living animal. Most animals actively search for or capture food to survive and reproduce (Pyke et al. 1977). Moreover, animals forage under multiple constraints, including high energetic costs (i.e., cost of movement and thermoregulation; Stephens and Krebs 1986). Energetic demands while foraging often represent substantial costs (e.g., Bozinovic and Vasquez 1999, Porter et al. 2002, Sears et al. 2006); thus, animals increase their chances of survival by minimizing energy expended and maximizing energy gained (Krebs et al. 1977). In temperate regions, animals need to cope with changing environmental conditions, seasonal reduction in food availability and inclement weather. This is the case for Glaucomys volans L. (Southern Flying Squirrel) in the northeastern US. Southern Flying Squirrels are small gliders found in the eastern US from Maine to Florida, and from the east coast to Texas (Sawyer and Rose 1985). Their wide range encompasses different habitats including deciduous forests and mixed woodlands (Bendel and Gates 1987). Southern Flying Squirrel populations adapted to colder conditions experience an extreme reduction in food availability during long winters (Stapp et al. 1991). The energetic costs of thermoregulation in cold environments are extensive (e.g., Conley and Porter 1986, Orr 1959, Orrock and Danielson 2009). Southern Flying Squirrels are known to store their food in tree cavities, under leaf litter and between branches, to avoid foraging during inclement weather (Helmick et al. 2014). They also form large social groups to maximize thermoregulation 1Department of Biological Sciences, State University of New York at Oswego, Oswego, NY 13126. *Corresponding author - maria.sagot@oswego.edu. Manuscript Editor: John Litvaitis Northeastern Naturalist 384 M.L. Nelson and M. Sagot 2018 Vol. 25, No. 3 (Stapp et al. 1991). However, despite evidence that high thermoregulation costs and food availability affect foraging decisions in cold temperatures (e.g., Kilpatrick 2003, Kotler et al. 1993, Meyer and Valone 1999), it is unclear how Southern Flying Squirrel populations inhabiting the northeastern US modify their foraging behavior to maximize survival. The aim of this study was to examine the effects of temperature and day length on the movement behavior of Southern Flying Squirrel. To minimize energy expended and maximize energy gained, we expected Southern Flying Squirrels to travel longer distances and expand their home ranges on warmer nights. Moreover, because food availability in the northeastern US increases during the growing season, we also expected increases in distance traveled and home range at longer day-lengths (when food is more abundant) and a subsequent decrease as days became shorter. Our results will provide a better understanding of how species modify their behavior to adapt to changing environmental conditions. Field-site Description We conducted this study at Rice Creek Field Station, located near the eastern end of the Lake Ontario coastal plain, Oswego, NY. Lake Ontario greatly affects local weather conditions, which include cool to mildly warm summers and long, cold, and windy winters with regular strong lake-effect snow storms. (Niziol et al. 1995). The average annual temperature is 8–9 °C, and the annual precipitation is 90 cm (Nelson 2009). The mature upland woods of the area include Acer (maple)– Tilia americana L. (Basswood) forests, especially in the coastal plains; and Fagus grandifolia Ehrh. (American Beech)–Maple communities and Quercus L. (oak)– Carya (hickory) communities in well-drained soils (Nelson 2009). The field station occupies ~130 ha of varied habitats including open fields, mature forests, and shrublands, representing several stages of succession. Most of the second-growth vegetation on the property is now 30–40 y old. Southern Flying Squirrels are commonly found on an area of old-growth hardwood (e.g., Acer saccharum L. [Sugar Maple], Prunus serotina Ehrh. [Black Cherry], Fraxinus americana L. [White Ash], Betula alleghaniensis Britton [Yellow Birch]) and conifer forest (e.g., Pinus [pine], Picea [spruce], Thuja occidentalis L. [Northern White Cedar]) forest that was maintained as a farm woodlot before the acquisition of the land (Nelson 2009). Methods Data collection began in April 2016 (based on when we caught the first individual) and ended in November 2016 (activity after this date decreased substantially), for a total of 32 tracking nights. To capture Southern Flying Squirrels for this tracking study, we trapped squirrels using Sherman traps (7.62 x 8.89 x 22.86 cm) placed on the ground (in this area, Southern Flying Squirrel is commonly trapped on the ground at an average rate of 7 individuals per day; M. Sagot, unpubl. data.) baited with peanut butter and oats. To obtain information on body condition, we weighed, sexed, and aged all the individuals trapped. We also attached a collar-mounted radio transmitter (Model PD-C2, Holohil Systems Ltd., Woodlawn, ON, Canada) Northeastern Naturalist Vol. 25, No. 3 M.L. Nelson and M. Sagot 2018 385 on 2 males and 3 females. Transmitter weight was 4 g (less than 4% of the average squirrel weight of 75.9 ± 7.76 g). To assess distance travelled and home range, we obtained 10 location fixes per individual, per night, during peak activity (defined as the first 3 h after sunset, as determined during a pilot study where we tracked individuals for 12 h), using 2 TR-4 radio receivers (Telonics, Inc., Mesa, AZ) for the duration of the study. We also recorded temperature (average temperature during radio-tracking periods) and day length, using the weather station at SUNY Oswego, Rice Creek Field Station. We used the arithmetic-mean estimator in LOAS software (version 3.0.1, Ecological Soft-ware Solutions, Urnäsch, Switzerland) to estimate fixed-point location. We calculated daily distance per individual by adding the distance between each of the 10 consecutive fixed-point locations, using the ruler tool in LOAS. To estimate home range, we used the home range extension (Rogers and Carr 1998) in ArcGIS 10, (ESRI, Redlands, CA), which creates minimum convex polygons and their respective area, based on the fixed-point locations. We employed the ANOVA function ‘aov’ in R (version 3.3.2; R Core Team 2013), to compare average distance and home range per individual. We used mixedeffects models to test the effect of temperature and day length on average daily distance traveled and home range. In the model, temperature and day length were fitted as fixed effects and individual was fitted as a random effect. To determine significance of effects, we used a log-likelihood ratio test following a χ2 distribution to compare a full model to a model where the effect of interest was removed. Degrees of freedom were equal to the difference in the number of parameters between the 2 models. We performed analyses in the package ‘lme4’ in R (version 3.3.2; R Core Team 2013). Results We followed each individual for 32 nights during the study period, for a total of 320 fixed locations per individual. During this time, temperature varied from 57.9 °C to 84.8 °C and day length varied from 10.45 h to 15.4 h. The average daily distance travelled per individual was 156.39 ± 32.18 m. All radio-tagged flying squirrels travelled similar distances while foraging (F 4,131 = 2.44, P = 0.118; Fig. 1a). They foraged longer distances in warmer temperatures (χ2 = 5.94, df = 1, P = 0.014; Fig. 2a) and at longer day lengths (χ 2 = 9.29, df = 1, P = 0.002, Fig. 3a). The average daily home-range per individual was 272.59 ± 40.59 m2. All radiotagged flying squirrels had similar home ranges over the course of the study (F4,129 = 2.44, P = 0.936; Fig. 1b). Southern Flying Squirrels increased their home range with temperature (χ2 = 5.59, df = 1, P = 0.018; Fig. 2b) and day length (χ2 = 7.07, df = 1, P = 0.007; Fig. 3b). Discussion The purpose of this study was to examine changes in the distance travelled and home range of Southern Flying Squirrels inhabiting the northeastern US. Our Northeastern Naturalist 386 M.L. Nelson and M. Sagot 2018 Vol. 25, No. 3 results suggest that Southern Flying Squirrels are able to alter their foraging behavior in response to temperature and day length to overcome the high energetic demands associated with thermoregulation and food availability. Gliding mammals, such as Southern Flying Squirrels, spend most of their daily energy foraging (Geiser and Stapp 2000). Foraging is energetically expensive because individuals need to travel between foraging patches (Geiser and Stapp 2000). If gliding individuals spend more time searching for foraging patches, they are negatively affected by the metabolic costs of recovery from the oxygen debt of locomotor activity (Gaesser and Brooks 1984). Thus, if Southern Flying Squirrels increase travel time between foraging patches, they should stay longer within Figure 1. (a) Average distance travelled and (b) home range of 5 Southern Flying Squirrels in Oswego, NY, from April to November 2016. Individuals 1 and 3 were males, and 2, 4, and 5 were females. Northeastern Naturalist Vol. 25, No. 3 M.L. Nelson and M. Sagot 2018 387 patches (Charnov 1976); however, this is not always possible in months when food is limited. It is not surprising that in this study, day length had the largest effect on distance travelled and home range. In the northeastern US, food is more abundant during the growing season, which corresponds to longer days (Stapp et al. 1991). If there is more food available, Southern Flying Squirrels are able to maximize energetic gain by obtaining abundant resources while foraging within patches, and thus, compensating for the energetic costs of travelling among patches. In addition to the costs associated with travelling within and between foraging patches, are those associated with thermoregulation (Kilpatrick 2003). A large body Figure 2. Effect of temperature on the (a) average daily distance travelled and (b) home range in Southern Flying Squirrels in Oswego, NY, from April to November 2016. Northeastern Naturalist 388 M.L. Nelson and M. Sagot 2018 Vol. 25, No. 3 of research has examined the effects of temperature on foraging behavior (e.g., Belovsky 1981, Bozinovic and Vasquez 1999, Bozinovic et al. 2000, Caraco 1979, Huey 1991). Animals foraging in low temperatures are negatively affected due to higher metabolic costs associated with maintaining homoeostasis (e.g., Kilpatrick 2003, Kotler et al. 1993, Merritt et al. 2001, Meyer and Valone 1999, Orrock and Danielson 2009). For instance, in temperate regions, Peromyscus leucopus Rafinesque (White-footed Mouse) foraging behavior is affected by relatively small changes in temperature (Orrock and Danielson 2009). Southern Flying Squirrels in central Mexico are also known to nest close to food sources to avoid traveling long distances when temperatures are colder than usual (Campuzano-Chavez-Peon et al. Figure 3. Effect of day length on (a) the average daily distance travelled and (b) home range in Southern Flying Squirrels in Oswego, NY, from April to November 2016. Northeastern Naturalist Vol. 25, No. 3 M.L. Nelson and M. Sagot 2018 389 2014). Thus, the effect of temperature on distance traveled and home range found in this study is likely associated to the energetic costs of thermoregulation, added to the high energetic demand of traveling within and between foraging patches. We sampled a small number of squirrels in our study; however, even with small sample sizes, we were able to determine significant effects of climate conditions on the foraging behavior of Southern Flying Squirrel. To our knowledge, this is the first to study to report how northern populations of Southern Flying Squirrels modify their daily movement and home range with changing environmental conditions in the northeastern US. Given the rapid and unpredictable changes in climate that we are currently experiencing, survival of mammalian species will in part depend on their ability to alter their foraging patterns and dispersal to track changes in suitable habitats (Loarie et al. 2009, Pearson 2006). Thus, it is imperative that we continue studying and understanding plasticity in foraging behavior and species’ ability to adapt to constantly changing environments. Acknowledgments We thank Rice Creek small grants for funding for the project. 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