ON THE EDGE OF EXTINCTION - A - THE TIGER (Panthera tigris)

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Title - 'HOME RANGE AND MOVEMENTS OF MALE TRANSLOCATED PROBLEM TIGERS IN SUMATRA'

Contributions - Pristna (D), Santosa (Y), Prasetyo (LB) and Kartono (AP)

Source - Asian Journal of Conservation Biology, Vol. 1, No.1, pp. 20-30, 2012

Abstract - In the last decades, the number of 'problem tigers' has increased significantly in Sumatra. Releasing these tigers back into the wild is a risk, as the behaviour of translocated tigers is poorly understood. In this study, the first of its kind in Sumatra, four male tigers, after they had been captured, rehabilitated and collared, were released 74 - 1350 km. from the capture site and monitored for a period of 79 - 253 days. The length of time needed to establish a home range varied between 6 - 13 weeks and home ranges varied between 67,1 - 400 square km.

Reason of capture - Three male tigers entered a village and killed domestic animals, after which they were captured. The fourth fell in a pitfall set up for deer.

Age and weight of the four male tigers - The oldest tiger was about 6 years of age and weighed 122 kg. Two others, both about 4 years of age, were 98 and 73 kg. The youngest male was about 2 years of age and weighed 75 kg. Their condition was described as 'good' when they were released.

Human-tiger conflict in Sumatra -  Nyhus and Tilson (2004) have collected scattered reports on human-tiger conflict. In the period 1978-1997, 30 humans were injured, whereas 146 were killed. In that period, 870 domestic animals were killed by tigers. Humans retaliated by killing 250 tigers. In the period 1998-2011, according to an unpublished report from the Sumatran Tiger Conservation Forum, tigers killed 326 domestic animals and 57 humans (81 were injured). As a result, 69 tigers were captured.

Previous translocations in Sumatra - Before this study, only 12 tigers have been translocated in Sumatra. One of these was trapped and killed 7 months after it was released back into the wild. A second tiger was found dead in a plastic rope snare (set up to capture a serow) only 6 days after it was released. A third tiger, an adult female, was recaptured after she had been seriously wounded. She had been released 3 months earlier.

Home range of male tigers in Sumatra - It was found that the home range of male tigers in Sumatra wasn't exclusive. An area occupied by one male " ... might also be used by another male at a different time ... " (pp. 24). Home ranges of male tigers in Sumatra show considerable variation in size.

Recommendation - " ... Thus, the conservation implication of this study is it might be best to translocate tigers to areas where there are very low tiger density, lowest possible human threats, and sufficient prey base, as well as a lot of access to water sources ... " (pp. 26).  

Comment - In a more recent study (2015) that will be discussed later, it was stated that Sumatra has about 250 adult tigers left. For this reason, releasing 'problem tigers' is important. The four males were monitored for 79-253 days after they had been released. Although one of them (the oldest male) killed a number of goats in the first two weeks, no problems were reported. It took the males 6-13 weeks to establish a home range. The study suggested that the rehabilitation succeeded in all respects. 

As to the weight of the four males. When I went over all skull measurements I have some time ago, I noticed distinct differences between age groups. Skulls of young adult tigers (4-5 years of age) are significantly longer and heavier than those of younger animals and skulls of male tigers of 6 years and older are longer and heavier than skulls of young adult males. The conclusion regarding age groups (in wild tigers) is supported by information on body length and weight: in general, mature animals (6 years and older) are longer and heavier than younger animals. What I found, was confirmed by the male tigers in this study. Apparently, there are no differences in this respect between tiger subspecies. Reply