Interpopulation and seasonal variations in habitat and microhabitat use of Vipera ammodytes

From Firenze University Press Journal: Acta Herpetologica

Angel V. Dyugmedzhiev, Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences

Borislav Y. Naumov, Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences

Nikolay D. Tzankov, National Museum of Natural History, Bulgarian Academy of Sciences

A species’ habitat is defined as the biotic and abiotic conditions that allow the survival and reproduction of this species (Hall et al., 1997; Morrison, 2009). A micro-habitat is a smaller-scale subset of a habitat, which rep-resents a specific place or a physical requirement of the species in a given habitat (Connell, 1961; Lugo et al., 1999; Petren, 2001; Bailey, 2009; Keith et al., 2020). A habitat can include several microhabitats, which may dif-fer in their structure or conditions (i.e., vegetation, light exposure, humidity, temperature, air circulation) (Connell, 1961; Lugo et al., 1999; Petren, 2001; Bailey, 2009; Keith et al., 2020). Therefore, when researching the spa-tial niche of a particular species, it is important to assess both its habitat and microhabitat requirements to bet-ter understand its utilisation of the environment. Such assessments are crucial for properly and effectively deliv-ering conservation actions on a target species.Many snakes are generally sedentary animals with low dispersal abilities so their distribution usually depends on both the climatic and habitat characteristics of the environment. The microclimatic and microhabitat conditions play a major role in snakes’ habitat selection (Vitt and Caldwell, 2014). For instance, the presence of stony microhabitats often plays a major role in the hier-archical selection of habitats as they provide snakes with favorable thermal conditions for thermoregulation and easy access to shelter from extreme environmental con-ditions or predators (Reinert, 1993; Kurek et al., 2018). Habitat use may vary across seasons, age groups, and populations of the same species, or depending on the reproductive status of individuals (Reinert, 1984, 1993;Sweet, 1985;Shine, 1986;Seigel, 1986; Burger and Zap-palorti, 1989;Luiselli et al., 1994; Charland and Gregory, 1995; Webb and Shine, 1998). Habitat use variability can be due to different factors, such as habitat and microhabi-tat availability, presence and location of suitable areas for hibernation and/or thermoregulation, or differences in food abundance between habitats (Reinert and Kodrich, 1982; Huey et al., 1989; Madsen and Shine, 1996). More-over, variability is also common in microhabitat use (Neumeyer, 1987; Brito, 2003; Martínez-Freiría et al., 2010;Strugariu et al., 2011).European vipers usually adhere to a certain small to medium-sized home range territory throughout most of their lives (Neumeyer, 1987; Naulleau et al., 1996; Saint Girons, 1997; Brito, 2003; Weinmann et al., 2004; Grait-son, 2008; Plasinger et al., 2014; Dyugmedzhiev et al., 2020). When hibernating sites, sites for thermoregulation, shelters from unfavorable climatic conditions or preda-tors, and a sufficient food base are all available within a given small territory, vipers can inhabit it throughout the entire activity period (Saint Girons, 1952, 1980; Neu-meyer, 1987; Naulleau et al., 1998; Thomas, 2004; Wol-lesen and Schwartze, 2004). However, places suitable for hibernation, those with high food availability or with suitable summer’ microclimatic conditions, often do not coincide. In such places, vipers conduct seasonal migra-tions from the hibernating areas to the summer habi-tats, and in autumn, they return to the hibernating areas (Duguy, 1963; Viitanen, 1967; Prestt, 1971; Saint Girons, 1980; Naulleau et al., 1998; Anderson, 2003; Wollesen and Schwartze, 2004; Graitson, 2008). The scales of these migrations depend on individual locality, with the biggest documented migrations being for Vipera berus (Linnaeus, 1758), from England and Finland, where some individu-als may travel up to 1.5–2 km from the hibernating areas to the summer habitats (Viitanen, 1967; Prestt, 1971).The nose-horned viper, Vipera ammodytes (Lin-naeus, 1758), is distributed from the western foothills of the Alps across the entire Balkan Peninsula and many Aegean islands to north-western and northern Asia Minor and the Lesser Caucasus (Speybroeck et al., 2016). Throughout its range, it inhabits a wide variety of habitats. However, the species is most frequently found in different types of open and sunny stony or rocky habitats with shrubs and grasses, also in differ-ent types of open deciduous forests (Tuleshkov, 1959; Bruno, 1967; Beshkov, 1993; Ioannidis and Bousbouras, 1997; Stumpel and Hahn, 2001; Heckes et al., 2005; Crnobrnja-Isailović et al., 2007; Plasinger et al., 2014; Mebert et al., 2015; Ghira, 2016). Within this wide vari-ety of habitats, however, nose-horned vipers usually adhere to stony and rocky microhabitats (Beshkov, 1993, Mebert et al., 2015; Ghira, 2016). The microhabitat type is considered one of the main determinants for popula-tion density of the species because optimal microhabitats provide more access to shelter and a richer food base for the vipers (Ghira, 2016). Despite the abundant data on the habitat use of Vipera ammodytes, most studies only describe the vari-ety of habitats in which the species is found. More com-plete studies, taking into consideration habitat availability, in order to evaluate the habitat preference of the spe-cies, are lacking. To date, the intraspecific variation (i.e., interpopulation or seasonal) in habitat and microhabitat use of the nose-horned viper also remains a poorly stud-ied topic, with data mainly on the seasonal variations in habitat and microhabitat use. In Serbia, Montenegro, and Northern Macedonia, males are usually detected in spring, exploiting open deciduous forests with southwest exposure; females are most often detected in summer, in rocky habitats with east and south exposure (Crnobrnja-Isailović et al., 2007). In Bulgaria, in early spring and late autumn, nose-horned vipers mainly inhabit rocky and stony sunny terrains with scarce vegetation (Beshk-ov, 1993). From the late spring until the beginning of autumn, vipers conduct short migrations to adjacent habitats, such as herbaceous vegetation, shrublands, and forests, often close to water sources (Beshkov, 1993). To date, there are no studies comparing habitat and micro-habitat use among different populations of the nose-horned viper.In Bulgaria, V. ammodytes is widespread throughout the country, except in the high mountains and urbanized or intensively cultivated agricultural lands (Stojanov et al., 2011). The current study aims to assess the general patterns of habitat and microhabitat use of V. ammodytes, based on habitat/microhabitat availability. In light of the available literature on vipers’ habitat and microhabitat use, and under the assumption that nose-horned viper habitat and microhabitat use can vary among populations, the following hypotheses were tested:

1. V.ammodytes prefers various stony and rocky habitats and microhabitats, overgrown with shrubs and herbaceous vegetation;
2. habitat and microhabitat preference are highly dependent on their respective avail-ability;
3. habitat and microhabitat preferences vary among different populations of V. ammodytes; 4) habitat and microhabitat use vary between the different seasons of the activity period.

DOI: https://doi.org/10.36253/a_h-15928

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