Factors driving Arabian gazelles (Gazella arabica) in Israel to extinction: time series analysis of population size and juvenile survival in an unexploited population

Abstract

Wild populations of Arabian gazelles (Gazella arabica) were once common on the Arabian Peninsula, but today disappeared from large parts of their former range. In Israel only a small population of currently 30 individuals survived, although it was-and still is-well protected from illegal hunting and habitat destruction. In our study we aimed to identify the factors influencing the population growth of G. arabica in Israel over the last two decades (1995-2017). We tested the impact of five environmental variables including annual mean maximum temperature, rainfall, the availability of two major food plants, competition with sympatric dorcas gazelle (G. dorcas) and predation (mainly by wolves) on two dependent variables relating to population viability (population size, percentage fawn survival) using a retrospective time series analysis. After testing for autocorrelations, two generalized least squares (GLS) models with autocorrelations at 3 and 6 years [GLS-AR(3, 6)] were identified as the best models to explain environmental effects on populations size. Wolf encounter rate had a significant negative effect on G. arabica population size, while G. dorcas population size had a significant positive effect, suggesting that wolf predation shapes the population size of both gazelle species. For percentage fawn survival, model residuals did not reveal any significant autocorrelation and the best fit GLS-AR(0) model retained only wolf encounter rate and mean annual maximal temperature as significant predictors. This result suggests a strong impact of wolf predation and increasing temperatures on the fawn survival of Arabian gazelles. Changed rainfall patterns, food availability and competition between gazelle species had no impact on fawn survival.

Early and late fawn mortality in a remnant population of Arabian gazelles (Gazella arabica)

“…Despite this population being protected from illegal hunting since 1955 (Clark and Frankenberg 2001), it has undergone a turbulent conservation history and has repeatedly faced local extinction (King et al 1993;Blank 1996Blank , 2000Blank , 2005. Several causes were proposed for the decline, including carnivore predation (mainly wolf, Canis lupus and golden jackal, Canis aureus; Shalmon et al 2020), competition with sympatric dorcas gazelles (Gazella dorcas; Breslau et al 2019), inbreeding (Hadas et al 2015) and climate change (Dolev and Perevolotsky 2004). Since 1965-the year when regular counts were introduced by the Israel Nature and Park Authority (INPA)-the population size experienced periodic undulations apparently related to the occurrence of wolves (Shalmon et al 2020).…”

“…Several causes were proposed for the decline, including carnivore predation (mainly wolf, Canis lupus and golden jackal, Canis aureus; Shalmon et al 2020), competition with sympatric dorcas gazelles (Gazella dorcas; Breslau et al 2019), inbreeding (Hadas et al 2015) and climate change (Dolev and Perevolotsky 2004). Since 1965-the year when regular counts were introduced by the Israel Nature and Park Authority (INPA)-the population size experienced periodic undulations apparently related to the occurrence of wolves (Shalmon et al 2020). Despite a considerable conservation effort and resource input by the INPA (i.e., predator culling, artificial water and food supply, irrigation, enclosure construction), the overall population trend continues to show a decline.…”

“…Monitoring the long-term reproductive success of females as well as the survival of their fawns is pivotal to understand the success (or failure) of the G. arabica conservation program in Israel. In their study on factors driving the Arabian gazelle in Israel to extinction, Shalmon et al (2020) used time series analysis to investigate population size and fawn survival in relation to the occurrence of wolves in the prime habitat of the gazelles. Their study suggested a strong impact of wolf predation on the gazelle population and a moderate effect of climate on fawn mortality, while competition and resource availability played only a minor role (but see Breslau et al 2019).…”

“…data). All fawns were born from 5 June 2006 to 20 September 2019, a period when the population was protected from wolf predation by a fenced enclosure (3.5 km 2 ; Shalmon et al 2020). Given that the enclosure protected the gazelles effectively from carnivore predation (data obtained during a period when the fence was collapsed were excluded from our analysis), we therefore rejected the probability that the high fawn mortality was due to predation (or indirect effects of predation such as stress, or trauma after hitting the fence).…”

“…Given that the enclosure protected the gazelles effectively from carnivore predation (data obtained during a period when the fence was collapsed were excluded from our analysis), we therefore rejected the probability that the high fawn mortality was due to predation (or indirect effects of predation such as stress, or trauma after hitting the fence). In their study, Shalmon et al (2020) investigated the fawn survival of G. arabica to the age of five months. In this study, we expanded our data set, also including the fawn survival to weaning age (3 months) and to reproductive maturity (12 months).…”