The Arabian gazelle Gazella arabica is a species of gazelle known from the Arabian Peninsula. Until recently, it was only known from a single lectotype specimen mistakenly thought to have been collected on the Farasan Islands in the Red Sea in A genetic study of the lectotype specimen revealed that skull and skin do not stem from the same individual but belong to two distinct lineages of the mountain gazelle Gazella gazella , necessitating restriction of the lectotype to the skin to conserve nomenclatural stability. A later study formalized the use of Gazella arabica for the Arabian lineage of the mountain gazelle, and synonymized Gazella erlangeri with G.
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We'd like to understand how you use our websites in order to improve them. Register your interest. 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. 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.
Wolf encounter rate had a significant negative effect on G. 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. Wild populations of desert ungulates have faced dramatic declines in past decades Durant et al.
Overhunting, but also habitat loss, desertification and climate change have contributed to this catastrophic loss Newby et al. The Arabian oryx Oryx leucoryx , for example, was eradicated in due to overhunting Henderson , but prior to extirpation in the wild, several captive breeding programmes were established to save the species from extinction Talbot ; Stanley Price Likewise, the conservation status of the Arabian gazelle Gazella arabica is alarming: once distributed from the Arava Valley in southern Israel along the mountains of western Saudi Arabia and Yemen into Oman and the United Arab Emirates, the species disappeared from large parts of its former distribution range Magin and Greth ; Thouless et al.
At present, a few isolated, natural or reintroduced populations persist Thouless et al. Currently, the world population of G. Currently, the population size is only 30 individuals this study.
Since the Arava population of G. Despite tremendous management efforts to reverse the decreasing population trend of G. Israel is the only country within the species distribution range, in which illegal hunting is not the main reason for its decline. Although illegal hunting has led to the current population size in Israel, the causes for the species decline in recent decades are rather natural than man-made and therefore represent an ideal study site to explore the vital causes for the species debility.
Essentially, five environmental variables, i. It was therefore predicted that high annual mean maximum temperatures and low precipitation negatively influence the population growth of G. It was also proposed that a high availability of two major food plant species positively affects the population growth of Arabian gazelles Breslau et al.
Competition for limited food resources with dorcas gazelles was also predicted to be a cause for the decline of G. Shalmon suggested that both species largely overlap in their dietary requirements, exploiting more or less the same two major food plant species.
We thus used the G. Predation, mainly by wolves, is considered to be another variable with negative impact on the G. Populations of canine predators in Israel have increased in recent decades, mainly due to foraging on human discard, unharvested or dropped agricultural products and undisposed carcasses of domestic livestock Shalmon ; Reichmann and Saltz ; Margolis et al.
In our study, we aimed to ultimately identify the factors that influence the population viability of G. To date this fenced area of natural habitat represents the last stronghold of G. Depending on soil salinity, the Yotvata NR comprises six vegetation belts Baharav , of which only the Vachellia formerly Acacia - Anabasis community occurs within the G. The community is dominated by Vachellia raddiana and V.
Annual herbs and grasses are scarce or even absent in this community Baharav The climate is hyper-arid with an annual mean temperature of Heavy, short rains cause flash floods that cross the G. In October and November , as well as in February , these flash floods destroyed the fence allowing wolves Canis lupus —the main natural predator of G.
In June , the fence was repaired and access for wolves prevented again Shalmon pers. The G. Until recently, G. Recent phylogenetic and morphological investigations, however, favoured the division of this species complex into two species: G. Until the G. The northern population was eradicated between and due to illegal hunting by soldiers of the Israeli Defence Forces Mendelssohn This small population experienced pronounced variation in population size, with maximum numbers never exceeding 68 individuals and a minimum population size of only 10 animals in and 11 in this study.
Since the population is restricted to its preferred habitat, i. The current population size in is 30 individuals, with 10 males, 13 females and 7 juveniles Shalmon pers. From to , annual counts of Arabian and dorcas gazelles Fig. After fencing in , total drive counts sensu Bothma were conducted within the G. Those gazelles trying to escape across the drive line between the vehicles were counted by one of the observers. Eye and radio contact between observers prevented double counting.
Since , two such counts were conducted; one in summer June—July , another one in winter December—February , and results were averaged across each year Fig. In the number of counts was increased to four, i. Moreover, due to long-term observations by INPA staff most adult females were individually known see below , contributing to the correct estimation of population size.
Based on known female-male and female-juvenile ratios Yom-Tov and Ilani ; Shalmon , the missing count result of was estimated as After , dorcas gazelles outside the enclosure were not considered. Percent fawn survival was calculated as the number of new-borns that survived for more than 5 months i. Month of birth and death were obtained during regular daily patrols in and around the enclosure carried out by INPA staff from to Fawns were identified through their mothers, who were individually known based on their characteristic face markings and horn shapes Fig.
Rainfall recordings were obtained from IMS , taken at Yotvata settlement, 1. The annual mean maximum temperature was calculated as the average of monthly January—December maximum temperatures for each year. From to the food availability of two major food plants was measured as Vachellia tortilis and V. Based on reference photos previously taken of both species in five different foliage stages, the greenness index was established by eyesight, using a green scale reaching from zero no foliage to five maximum foliage.
To determine greenness, photographs of both species were taken once a year in autumn at the beginning of the rainy season, using the same camera, location, distance, angle and camera settings.
Average greenness was established for 30 trees of each species and then summed to obtain an overall greenness index for both species in each year. Missing values, from to , were interpolated from adjacent values, i.
Both, G. Competition with G. From to both species were counted as described above Yom-Tov and Ilani In the Yotvata NR, wolves represent the only predator of both gazelle species Shalmon Leopards Panthera pardus nimr are locally extinct, and caracals Caracal caracal , golden jackals Canis aureus and striped hyenas Hyaena hyaena occur only sporadically in the study area. Red foxes Vulpes vulpes may scavenge on gazelle carcasses and afterbirths, but are too small to actively prey on gazelles Mendelssohn ; Shalmon pers.
From to a wolf encounter rate was established as a proxy of predation pressure in the respective year. After fencing the G. To avoid overestimation of wolf encounter rates obtained from camera trapping, pictures taken on the same day were counted as only one encounter, unless two or more individuals were trapped on the same image Fig.
Individuals could not be distinguished by either survey method and wolf encounter rates may thus be biased by repeated sightings. In all cases, measurements were averaged across samplings to obtain one value for each year — To achieve normal distribution, all absolute data, i. Relative data such as percentage fawn survival were arcsine square root transformed. In case autocorrelated errors were detected, coefficients were estimated for the first-order Autoregressive model AR 1 in combination with Restricted Maximum Likelihood REML of variance components.
All environmental variables, as well as their two-way interaction terms were included in the initial model but removed using a stepwise backwards elimination procedure, to identify the best fit model with the smallest AIC and lowest residual standard error SE.
Unstandardized beta B , t-test statistics t and variance inflation factor VIF were established and applied as described in Pinheiro et al. Inspection of model residuals did not indicate violations of model assumptions, i. All data analyses were carried out in RStudio version 3. After applying a stepwise backwards elimination procedure, only wolf encounter rate and G.
Both final models revealed that the wolf encounter rate had a significant negative relationship with the G. S2b, c. Percentage fawn survival of the G. However, at this point it should be also highlighted that a fenced population containing only 30 individuals is not ideal to examine natural processes. Five environmental variables were tested for their effects on two dependent variables representative for population viability i.
This is surprising since it was predicted that Arabian gazelles compete with sympatric dorcas gazelles for limited food resources Shalmon , Instead, it rather appears that the population growth of both species is subject to the same environmental stressors, i.
Resource partitioning and reduced competition were reported from other ungulate communities such as swamp deer Cervus duvauceli and hog deer Axis porcinus , two sympatric deer species from Nepal that consumed almost equal proportions of the same woody browse species Wegge et al.
Here, niche segregation has developed among grazing ungulates, allowing a relaxed co-existence but facing a similar predation pressure Sinclair ; Putman ; Arsenault and Owen-Smith Our result unrevealed not only a similar predation pressure on both gazelle species, but also two periodic population cycles, i.
Such fluctuating population size patterns are known from other coupled predator—prey cycles e. Likewise, predators consume more prey items per capita when prey densities are high and less when prey densities are low Adamcik et al. Unless further time series analysis include longer sampling periods to confirm such a cycle, this remains speculative and possibly biased by management actions such as culling of wolves and fencing the prime habitat of the gazelles.
Finally, food availability, measured as Vachellia greenness, and rainfall had no significant effect on the G. This finding corresponds to our results on population size, providing another strong argument that wolf predation shapes the G.
Gazella arabica - #2113
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