Preliminary Evidence of a Barrier Effect of a Railroad on the Migration of Mongolian Gazelles

Abstract

Much remains to be learned about how anthropogenic structures affect migration in large mammals. We examined the potential influence of the international railroad in Mongolia on migration in Mongolian gazelles (Procapra gutturosa). We examined gazelle movements and the normalized difference vegetation index (NDVI) on both sides of the railroad. The tracked gazelles never crossed the railroad, despite movements that mainly followed the railroad in winter and higher NDVI values on the opposite side. It is likely that the railroad had a barrier effect on gazelle migration because it split the gazelles' habitat. Our results, although based on an extremely small sample, have utility in indicating approaches that might be useful for examining migration in ungulates.Resumen: Falta mucho por conocer sobre el efecto de estructuras antropogénicas sobre la migración de mamíferos mayores. Examinamos la potencial influencia del ferrocarril internacional en Mongolia sobre la migración de gacelas de Mongolia ( Procapra gutturosa). Examinamos los movimientos de las gacelas y eĺ ındice de vegetación de diferencia normalizada (IVDN) a ambos lados de la vía férrea. Las gacelas rastreadas nunca cruzaron la vía férrea, a pesar de que los movimientos mayormente seguían la vía en invierno y que los valores de IVDN eran mayores del lado contrario. Es probable que la vía férrea produjera un efecto de barrera sobre la migración de las gacelas porque dividió al hábitat de las gacelas. Nuestros resultados, aunque basados en una muestra extremadamente pequeña, sonútiles para señalar estrategias que pueden ser utilizadas provechosamente para examinar la migración de ungulados.

Habitat Fragmentation by Railways as a Barrier to Great Migrations of Ungulates in Mongolia

“…These zones spanned most northern and southern gazelle locations observed during the winter. We detected a significant gradient of NDVI values from 17 November to 2 December 2002, the period when the gazelles moved the greatest distance, from southwest to northeast (Ito et al 2005). The highest average NDVI value was in the 30-to 60-km northeastern zone (Fig.…”

“…The two gazelles captured near the railway moved along it for a year, but never crossed it (Ito et al 2005). They moved closer to the railway during winter (October-March) than during summer (April-September), and the nearest distances of the two gazelles to the railway were 0.3 and 1.8 km, respectively (Fig.…”

“…Tracked Mongolian gazelles and Asiatic wild asses used areas far from the barriers during summer but used areas close to the railway and the borders during winter ( Fig. 14.7; Ito et al 2005Ito et al , 2013a. The only case of a tracked wild ass crossing the border to China and returning to Mongolia was observed during the harsh winter (Kaczensky et al 2011a), but no other tracked animals ever crossed it.…”

“…Animals can suffer mortality directly when crossing the railway or indirectly because of barrier effects that prevent them from reaching suitable sites for food, water, and reproduction. These concerns led to animal tracking studies (e.g., Ito et al 2005Ito et al , 2013a. Mammals inhabiting the grassland ecosystems of Mongolia and showing long-distance movements that are potentially affected by the railway are the Mongolian gazelle, the goitered gazelle, and the Asiatic wild ass ( Fig.…”

“…We first conducted satellite tracking of Mongolian gazelles in 2002 (Ito et al 2005(Ito et al , 2006. In October 2002, two female gazelles were captured on the southwestern side of the railway and collared with a satellite transmitter.…”