Abstract
The Sumatran Rhinoceros Dicerorhinus sumatrensis is on the edge of extinction. The decline of this species was initially attributed to poaching and habitat loss, but evidence presented here indicates that reproductive failure has also been a significant cause of loss, and continues to affect wild populations. Indonesia’s remaining populations of Sumatran Rhino are small and scattered, with limited access to breeding opportunities with unrelated mates. This leaves them subject to inbreeding and isolation-induced infertility, linked to fertility problems analyzed here. Sumatran Rhino females in captivity showed high rates (>70%) of reproductive pathology and/or problems with conception, which has significantly hindered the breeding program. Technological advances enabling examination immediately after capture revealed similarly high rates and types of reproductive problems in individuals from wild populations. The last seven Sumatran Rhino females captured were from areas with small declining populations, and six had reproductive problems. Going forward, capturing similarly compromised animals will take up valuable space and resources needed for fertile animals. The high risk of infertility and difficulty of treating underlying conditions, coupled with the decreasing number of remaining animals, means that the success of efforts to build a viable captive population will depend upon utilizing fertile animals and applying assisted reproductive techniques. Decades of exhaustive in situ surveys have not provided information relevant to population management or to ascertaining the fertility status of individual animals. Thus the first priority should be the capture of individuals as new founders from areas with the highest likelihood of containing fertile rhinos, indicated by recent camera trap photos of mothers with offspring. In Sumatra these areas include Way Kambas and parts of the Leuser ecosystem.
Highlights
The high rate of pathologic abnormalities observed in the reproductive tracts of female rhinos from both Indonesia and Malaysia was initially presented at the 1999 Asian Rhino Specialist Group Meeting, and published shortly thereafter (Schaffer et al 2002)
This paper is based on records of female Sumatran Rhinos captured or poached from various sites in Indonesia and Malaysia between 1984 and 2018
The critically low estimates of numbers in widely scattered populations of the Sumatran Rhino, coupled with the fact that both captive populations and animals caught from the wild are largely reproductively compromised, means that only a small number of reproductively viable animals may be left in the wild
Summary
SchafferThe global population of Sumatran Rhinoceros Dicerorhinus sumatrensis was estimated at less than 100 individuals at the Sumatran Rhino Crisis Summit of 2013. Indicates that reproductive failure (previously only associated with captivity) is an important factor in the continued decline of this species. The prevalence of reproductive problems across time and landscapes indicate a need to understand the scope and nature of this failure for successful recovery. The husbandry of this species was poorly understood and insufficient knowledge about diet, habitat, social structure, mating behavior, and reproduction hampered breeding efforts. Introductions of males and females often led to violent responses. These husbandry gaps resulted in significant losses in the initial captive population. The high rate of pathologic abnormalities observed in the reproductive tracts of female rhinos from both Indonesia and Malaysia was initially presented at the 1999 Asian Rhino Specialist Group Meeting, and published shortly thereafter (Schaffer et al 2002). Pregnancy failure was linked to early embryonic death (Roth et al 2001)
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