Endangered species’ trait responses to environmental variability in agricultural settings

Abstract

Understanding the spatial and temporal effects of variable environmental conditions on demographic characteristics is important in order to stop the decline of endangered-species populations. To capture interactions between a species and its environment, in this work the demographic traits of the European ground squirrel (EGS), Spermophilus citellus, were modeled as a function of agricultural landscape structure. The habitat suitability index was determined for 20 localities within the study area based on habitat use, management and type. After mapping the habitat patch occupancy in the field, crop cover maps, the average normalized difference vegetation index (NDVI) and automated water extraction index (AWEI) were obtained from satellite images covering the period 2013-2015. This data was used to develop population-level generalized linear models (GLMs) and individual-level conditional mixed-effects models (GLMMs) in R package Ime4, focusing on the key demographic traits of the EGS. The land composition and patch carrying capacity (PCC) are the key determinants of the endangered EGS population size, while system productivity is the main factor influencing individuals' body condition after monitoring for variations across sampling years and age classes. The proposed landscape structural models show that human activities and abiotic factors shape the demographic rates of the EGS. Thus, to conserve threatened species, an appropriate focus on the spatial adaptation strategies should be employed.

Distribution, Population Size, and Habitat Characteristics of the Endangered European Ground Squirrel (Spermophilus citellus, Rodentia, Mammalia) in Its Southernmost Range

“…This relation indicates that the type of land use plays an important role for the ecological functions of the ecosystems, which is more marked in the Mediterranean climate [62]. Moreover, an increase in vegetation productivity most likely affects ground squirrels via changes in vegetation height and, consequently, foraging activity [63,64]. The combination of an arid Mediterranean climate and intense habitat management resulting in sparse vegetation (low NDVI) could influence the home range of individuals, which try to surpass the food limitations by foraging in larger areas in poor environments [14,65,66].…”

Diet of the European ground squirrel (Spermophilus citellus) in the southern Pannonian plain

“…The latest assessment emphasizes land conversion and infrastructural development, along with the abandonment of traditional management practices, as the main drivers of its habitat fragmentation and consequent population decline. Based on the latest studies, these adverse conditions are also found in Serbia, and demand immediate conservation actions [15,[21][22][23][24].…”

“…The species' range in Vojvodina has shrunk by 70% compared to the available historical data, and about half of the populations presently reside outside the protected area network [23]. To halt and potentially reverse the local population decline caused by anthropological activities and environmental variability, adequate habitat management plans and programs need to be established [24]. Detailed studies regarding habitat conditions and feeding habits are an important structural component of local habitat management plans and programs.…”