Using microclimate of arid landscape as a resource in goitered gazelle comfort behavior

Highlights

• Goitered gazelle males used more elevated windier areas during hot weather.

• Females and especially fawns preferred shade of shrubs/trees during summer.

• Smaller fawns stayed in shade more often than adults.

• Goitered gazelles seek windless places during cold months.

• Goitered gazelles used landscape features for effective body thermoregulation.

Abstract

Animals living in desert environments have to be adaptable to significant temperature shifts in their surroundings. Ungulates have behavioral adaptations to adjust to thermoregulation problems and use the landscape features to lessen the effects of thermal fluctuations. In this paper, I investigated the usage of the local landscape by goitered gazelles (Gazella subgutturosa) in natural conditions to better understand behavioral adaptations of wild species to a northern arid environment. I found that during the hottest weather, goitered gazelle females and fawns used the shade of vegetation more often than males, while males preferred more elevated, windier places; while during winter, goitered gazelles of both sexes used deep, dry river beds in the foothills as a shelter against the strong winds in winter and early-spring. Body orientation with of pointing the hindquarters toward the wind was used infrequently than other protective behaviors. The sands of dry river beds were the most selected places for goitered gazelles to rest all year round, especially during the cold season. Using the microclimate features of the landscape is a very important part of the goitered gazelles’ adaptations, which help to reduce the costs associated with body thermoregulation and to endure the heavy heat load during summers and the severe harsh cold during winters.

Introduction

Deserts are characterized by high air temperatures, strong solar radiation, and a lack of water and cover (Southgate et al., 1996; Mader et al., 2010). Therefore, body thermoregulation and a deficit of water are the most important challenges for desert animals (Feldhamer et al., 1999). Overheating, for example, has a negative impact on fertilization and milk production (West, 2003; Souza et al., 2005). The inability to reduce the heat load leads to an increase in core body temperature and dehydration with the possibility of either or both conditions reaching lethal levels (Curtis, 1983). In cold conditions, warm-blooded animals strive to keep the stability of their body temperature by using systems of thermo-isolation and thermoregulation. In addition to physiological mechanisms, ungulates can use features of their local landscape, such as foothill gorges, deep dry river beds, high dunes and thickets of trees and shrubs for protection against strong cold winds (Zhevnerov et al., 1983; Blank, 1990).

Maintenance of body temperature within a narrow range is essential to proper metabolic function in mammals, and deviations outside a narrow range triggers thermoregulatory responses (Sessler, 1997). Indeed, investigations of many ungulate species demonstrated that their core body temperatures fluctuated within very narrow limits (less than ±2 °C) (Sargeant et al., 1994; Fuller et al., 2005). To facilitate this balance, animals have three kinds of mechanisms ̶ physiological, morphological and behavioral - to deal with maintaining body temperature within acceptable limits and minimizing water loss (Cain et al., 2006). However, production efficiency is better when animals do not need to use the physiological mechanisms (Souza et al., 2005); therefore, the key to ungulate thermoregulation, in the face of daily and seasonal changes of ambient temperature, appears to lie not in physiological mechanisms, but rather in their ability to employ behavioral thermoregulation (Fuller et al., 2005). First, free-living, terrestrial animals that select more favorable microclimate sites or a shelter in thermally heterogeneous habitats can change the timing of their activities, diet selection, social behaviors, body orientation, migration, and timing of reproduction (Bartholomew, 1987; Huey, 1991). Shade, as protection from extremes in weather, is required by animals, and they search for more comfortable sites, using features of the micro-relief in their environment, and looking for a fresh or humid place (Holcomb, 2017).

In contrast to physiological and morphological mechanisms, which have been considered for many species of wild and domestic ungulates (Hofmeyr, 1985; Fuller et al., 1999, 2005; Maloney et al., 2002), behavioral responses of wild ungulates to weather extremes have not been studied sufficiently (Cain et al., 2006; Cook et al., 2007), while using habitat characteristics for more comfortable sites by goitered gazelles (Gazella subgutturosa) has not been observed at all. The focus of this paper is the behavioral responses of goitered gazelles in natural conditions to hot sunny weather and cold windy weather and using the microclimate features of landscape, including shady and windy sites during the hot months and wind-protected, sunny places during the cold months.

During hot weather, shade from vegetation cover reduces ambient temperature and provides a reduced heat load (Demarchi and Bunnell, 1993). Therefore, there is a strong linear relationship between the use of shade by ungulates and both ambient temperature and incident solar radiation (Jarman and Jarman, 1973). Also the study of domestic horses has shown that the use of shade or shelter in hot weather does not correlate with sex (Heleski and Murtazashvili, 2010; Holcomb et al., 2014; Holcomb and Stull, 2016). So based on this observation, I thought that the same would be true for goitered gazelles and proposed my first hypothesis that shade-seeking behavior would not be correlated with sex and both males and females would use the shade equiprobably.

Young horses (foals and yearlings) were found to be more likely to seek shade in hot weather, because smaller body sized animals are more vulnerable to overheating, since an animal's heat load is proportional to its surface area rather than to its body weight, and smaller individuals have a relatively larger body surface compared to larger ones (Heleski and Murtazashvili, 2010). According to these observations I proposed my second hypothesis that young goitered gazelles also would be more likely to seek shade during hot months than adults.

During the cold months in Central Asia (winter and early-spring), ungulates in arid areas used deep depressions and dry river beds and foothills for protection against strong, cold winds (Sludskiy, 1963). In addition, during the cold daytime hours, wildebeest (Connochaetes taurinus) oriented their bodies in a “tail-to-wind” posture, then as the temperature rose, they changed their position to face into the wind (Berry et al., 1982; Maloney et al., 2002). Based on these observations, I suggested my third hypothesis that during cold seasons goitered gazelles would select windless slopes for their rest and they would use deep river beds and mountain gorges for protection against winds; they would also orient their bodies “tail-to-wind” to stay more comfortable during cold winds.

Domestic cows have been found to rest longer on a softer floor (Herlin, 1997; Chaplin et al., 2000), and the health of their legs improved through exposure to sand-covered floor stalls (Haley et al., 2001). I suggested that the same behavior would be observed in goitered gazelles and proposed my fourth hypothesis that goitered gazelles would choose the softer sand floors of the dry river beds for resting than the harder grounds surrounding the dry river beds.