Density, age and sex structure of goitred gazelle (Gazella subgutturosa) in Golestan National Park

The goitred gazelle, which is classified as a vulnerable species (VU) by IUCN has a very wide distribution across the Middle East, Pakistan, Central Asia, China and Mongolia. A few ecological studies have been conducted on some aspects of goitred gazelle, such as population dynamics, habitat selection, daily activity, and social organization. However, little is known about the population dynamics of Goitred gazelle in Iran. Among the artiodactyls in Golestan National Park, goitred gazelles have shown the most vulnerability to the poaching and increasing frequency and intensity of habitat destruction. The objective of this study was to determine the population dynamics of goitred gazelle in different areas of Golestan National Park. Fieldwork was carried out in Golestan National park, Iran. The transect line sampling method was used to survey the population dynamics of goitred gazelle, during the survey at each of the 24 transects, over three visits conducted between February 2016 and July 2016. Data (number of individuals, sex and age of gazelles) were collected at each of 24 transects. To calculate the density of gazelles we used the DISTANCE 6.0 programme. Differences in the lambing rate were evaluated using the non-parametrical Kruskal-Wallis and Mann-Whitney U-test. All the statistical tests were performed using Minitab 15 and Ecological Methodology software. Results of the density analysis showed that goitred gazelles had the largest and the smallest population sizes in Kohne Mirzabaylu and Rabat, respectively. The sex ratio varied from 1.33 to 1.86; moreover, results of the sex ratio showed that the Almeh and Soulgerd populations had the best sex ratio. The number of middle-aged and older males was low in all gazelle populations which means that a high proportion of females prone to fertility were unable to mate. Many management strategies offer an increase in mature males in the population which results in increases in the reproduction rate of females (Bender, 2002). Due to the low numbers of qualified females (6 years old and older), a considerable number of females could not mate. This means the males spend more time gathering the females and warding off rival males and, consequently, the female reproduction rate decreases. Yearlings (male and female) and very old gazelles (more than 11 years old) comprised the highest and the lowest percentages of the gazelle population, respectively. The highest percentage of lambs occurred in the Soulgerd and Kohne Mirzabaylu populations. This pattern of age class in lambs was due to high security in the vicinity of these two areas from wildlife guard stations. There was no significant difference among different areas in lambing rate. This pattern was consistent with Varasteh (2004). According to this study conducted on the sex and age structure, lambing rate, and density of gazelles in comparison with the past, it is quite obvious that the current trend of population dynamics is in decline and this is an alarm that indicates the need for urgent action to reduce the speed of population decline and for careful and long-term planning to management of gazelles populations.