Digestive physiology and movement patterns of animal dispersers determine deposition patterns for endozoochorously dispersed seeds. We combined data from feeding trials, germination tests, and GPS telemetry of Asian elephants (Elephas maximus) to (1) describe the spatial scale at which Asian elephants disperse seeds; (2) assess whether seasonal differences in diet composition and ranging behavior translate into differences in seed shadows; and (3) evaluate whether scale and seasonal patterns vary between two ecologically distinct areas: Sri Lanka's dry monsoon forests and Myanmar's (Burma) mixed‐deciduous forests. The combination of seed retention times (mean 39.5 h, maximum 114 h) and elephant displacement rates (average 1988 m in 116 hours) resulted in 50% of seeds dispersed over 1.2 km (mean 1222–2105 m, maximum 5772 m). Shifts in diet composition did not affect gut retention time and germination of ingested seeds. Elephant displacements were slightly longer, with stronger seasonal variation in Myanmar. As a consequence, seed dispersal curves varied seasonally with longer distances during the dry season in Myanmar but not in Sri Lanka. Seasonal and geographic variation in seed dispersal curves was the result of variation in elephant movement patterns, rather than the effect of diet changes on the fate of ingested seeds.
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 loss and habitat fragmentation caused by anthropogenic activities are the main factors that constrain long-distance movement of ungulates. Mongolian gazelles (Procapra gutturosa) and Asiatic wild asses (Equus hemionus) in Mongolia are facing habitat fragmentation and loss. To better understand how their movements respond to potential anthropogenic and natural barriers, we tracked 24 Mongolian gazelles and 12 wild asses near the Ulaanbaatar–Beijing Railroad and the fenced international border between Mongolia and China between 2002 and 2012. None of the tracked gazelles crossed the railroad, even though gazelles were captured on both sides of the tracks at the start of the study. Similarly, we did not observe cross-border movements between Mongolia and China for either species, even though some animals used areas adjacent to the border. The both species used close areas to the anthropogenic barriers more frequently during winter than summer. These results suggest strong impacts by the artificial barriers. The construction of new railroads and roads to permit mining and other resource development therefore creates the threat of further habitat fragmentation, because the planned routes will divide the remaining non-fragmented habitats of the ungulates into smaller pieces. To conserve long-distance movement of the ungulates in this area, it will be necessary to remove or mitigate the barrier effects of the existing and planned roads and railroads and to adopt a landscape-level approach to allow access by ungulates to wide ranges throughout their distribution.
We examined the distribution patterns of native animals on Amami-Oshima Island, southern Japan, along a historical gradient of mongoose establishment and estimated the effects of mongoose on the native fauna. To assess the relative abundance of various grounddwelling animals, we used the following four methods; sensor cameras for exotic mammals, nighttime driving census for nocturnal native vertebrates, line census for ground-dwelling lizards, and adhesive traps for arthropods. The results indicated that seven species with larger body size, including mammals, birds, reptiles, and amphibians, were rarely observed in mongooseinfested area. By contrast, medium-sized animals showed neutral relationships with mongoose establishment. Interestingly, the densities of smaller-sized animals were higher in mongooseinfested area. It could be interpreted that smaller species have increased in abundance through topdown cascades, i.e., decreases in native predators such as frogs and lizards caused by the mongoose have resulted in increases in the abundance of smaller animals. Predation pressures by mongoose and native predators may be canceled out for medium-sized animals, causing neutral responses to mongoose by these animals. This study appears to be the first example that shows the influence of mongoose on a wide variety of native animals. In addition, our findings indicate the importance of considering the food web structure of a recipient ecosystem and contribute to the prediction and assessment of ecological risks caused not only by mongoose, but also by other invasive top predators.
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