|Tuesday, 12 October 2004|
Homing in on elephant ranging patterns
by Tharuka Dissanaike
It was a surprising discovery. One that challenged assumed patterns and accepted norms. But Sri Lankan elephants, really, do not 'migrate'. Quite contrary to popular belief, elephants do not walk down from the northwest to the north central and then to the south for food or for mating.
Sri Lankan elephants in fact, have small home ranges compared to their cousins across the Palk Strait and even more so, in comparison to the distant relatives out in Africa.
When a team of young scientists decided to monitor ranging behaviour of elephants in two locations of Sri Lanka, they did not expect to come up with information that is so drastically different from what is known and accepted today.
But after eight years of monitoring several radio-collared animals, and study of elephant ecology, the research team is ready to make a statement. Sri Lankan elephants range over relatively small areas and certainly do not undertake 'long-range cross-country migrations'.
What's more, the elephants studied by this team, generally stayed loyal to their chosen home range year after year. Again contrary to belief, there was no distinct seasonal migrations to distant locations -although it was observed that the elephants foraged in different areas within their home range during dry and rainy seasons.
"Earlier studies have all been based on eye-witness reports of animals with certain physical characteristics. This is a difficult method that does not guarantee accuracy," said Dr. Devaka Weerakoon of the University of Colombo and a key team member. "We used radio telemetry to obtain daily locations of the collared animals and this gave us a fairly accurate idea of their ranging pattern over several years."
The team comprising Dr. Prithiviraj Fernando, Dr. Devaka Weerakoon, Dr. Eric Wikramanayake, Ms. Manori Gunawardene, L.K. Jayasinghe, H.K. Janaka and Rahula Perera, assisted by G.V. Gunawardene and Nimal Kaluarachchi from the DWLC, (Department of Wildlife Conservation) tracked 18 elephants in two very different locations in the country- the southeast (in and around Yala and Lunugamvehera National Parks) and the northwest (outside Wilpattu along the Puttlam-Anuradhapura road).
The first animals were collared back in 1995. The collared elephants included six males and 12 females.
The scientists found that females had smaller range areas. They generally moved in groups and their home ranges measured between 30 square kilometres and 160 square kilometres.
Males, generally being loners, ranged between 53 to 346 square kilometres. While the home ranges of males were much smaller than those of the female herds over most of the year, they dramatically expanded their range during musth.
In contrast, South Indian elephants are known to have home ranges that exceed 500 square kilometres and to move over long distances seasonally. African elephants in the arid Namibian desert have home ranges over 20,000 square kilometres and travel vast distances between feeding grounds, although in other parts of Africa, scientists are now beginning to find patterns similar to Sri Lanka.
The scientists found that some elephants moved solely inside protected areas (National Parks, Sanctuaries, Forest Reserves etc), while others ranged totally outside of these demarcated areas. Some, however, moved in and out of protected areas as their regular ranging behaviour.
This, especially the fact that many elephants today range outside national parks, presents a very real problem for conservation. Long term plans of pushing all elephant herds into protected areas and containing them there by electric fences or other such methods appears to be a Herculean if impractical solution.
Many of the existing electric fences around national parks have elephants on both sides of the fence. Fences also obstruct the natural ranging pattern of those elephants using both protected areas and outside habitat.
Besides, pushing in more elephants than the parks can support would inevitably jeopardize the survival of the elephants that live within the parks, which have a good prospect for survival.
Weerakoon said that they saw distinct differences in the ranging behaviour in the two study locations. "In the south and east of Sri Lanka, there is still a large extent of land outside protected areas in scrub forests.
Here, the density of people and settlements is not so high. But in the northwest, the situation is different. There are few protected areas except for Wilpattu, and most elephants live outside of national parks, in areas developed under irrigated agriculture."
In the northwest, which is today a mosaic of irrigated paddy land, small forest patches, new settlements, towns and irrigation reservoirs, elephants and people live in the same mix of habitat. Here, loss of forest has fragmented the habitat of elephants. Studies showed that elephants range in larger areas and into crop fields and villages.
In these areas, naturally, the human-elephant conflict is very high. While in the south, female groups generally shied away from human presence and lone males were blamed for crop losses; in the northwest, both males and female groups raided fields and villages. This is due to the high number of humans and elephants forced to live together in an altered landscape adequate forest areas for elephants.
Looking collared animals' behaviour, the team also felt that when food and water is adequately available, elephants confine their home range to a smaller area and generally stick to their adopted range. For food, elephants preferred secondary or scrub forest to mature tall forests.
In the boundary areas of Yala National Park, elephants loved to forage in abandoned chena fields, devouring the remaining vegetable matter and new shoots that came up in the fallow period. Because the fields are fallow, there is no conflict with humans. "This allowed temporal resource partitioning between elephants and people, and perhaps provided a way they could co-exist," said Dr. Eric Wikramanayake.
This brought to light another fact-elephant herds mainly determine their home range on the basis of food and water availability. Food, more than water, since the dry zone of Sri Lanka is littered with small tanks and water is rarely a problem. An elephant can 'fill up' for the day in a few minutes; hence can walk a long distance to water.
However, to obtain the requirement of food around 150 Kg a day, an elephant needs to eat for about 17 hours a day.
If there is sufficient food their range will be small. Where there is loss of habitat and opportunities for gathering food are limited, they expand the range area. In areas that are highly populated by people, elephants generally increased their home range by three fold or more.
Collared elephants that lived among human populations ranged over a larger area (150-185 square kilometres) as opposed to those elephants inhabiting areas with low human density (48-53 square kilometres). Studies on the genetics of elephants have shown that the Sri Lankan elephant has evolved into distinct populations in different parts of the country with little mixing.
The northern/ northwestern populations are distinct from the central-eastern populations and southern populations. These differences are apparent even in their body shapes- the southern elephants being shorter in stature so called Ruhunu Gataw - and the vil aliya of the central/eastern area being much larger with a massive head.
Although not accepted now, the distinctness of the vil aliya led to it being classified as a different subspecies by an eminent Sri Lankan scientist, Deraniyagala in the 1940s.
Although the differences are not adequate to classify them as subspecies, recent studies by Dr Prithiviraj Fernando indicates that there is some genetic differences within the populations to suggest that the populations have been separate.
In others words, Sri Lankan elephants have always had small home ranges and did not migrate. Translocating animals across the country and between areas for elephant control in mitigating human elephant conflict, would wipe out such regional differences in elephants.
The research on ranging patterns and ecology of elephants is being continued through the Centre for Conservation and Research. The Centre hopes to collaborate with the Department of Wild Life Conservation, Conservation NGOs and other scientists to develop a management plan for Sri Lankan elephants.
"We hope this research and future findings, will contribute towards elephant conservation and efforts to mitigate human elephant conflict," said Chairman of CCR, Dr. Prithiviraj Fernando.
Bull elephants in musth showed very different ranging behaviour. During periods of musth, elephants increased their home range dramatically. Musth is a condition that is peculiar to adult male elephants, brought on by hormonal changes. An increase in testosterone is believed to cause musth symptoms.
During this period of about two months a year their behaviour completely changes, they become more aggressive, there is a discharge from the temporal glands, and they continuously dribble urine.
Radio tracked males increase their area of activity as much as four times their normal range during musth. This behaviour seems to be linked to reproduction and is quite likely a mechanism to prevent inbreeding among related individuals.
The Galge male (red coloured range) was one of the first elephants to be collared. An adult male, in the prime of his life, he roamed around the Buttala-Kataragama road most of the year, feeding in the grassy patches along the road.
On a couple of occasions, when the team was tracking him, the signal seemed to be coming from the middle of the village area close to Kirivehera. The scientists were concerned that the collar had fallen off and maybe someone picked it up and brought it to the village.
However, upon homing in, they found to their amazement, that he was just resting inside a tiny patch of community forest (beheth kele) right in the middle of the village, with no one in the village having the faintest idea that there was an elephant right in their midst.
For most of the year, he had a very small home range of 10-20 square kilometres, but when he came into musth in February-March, his range increased enormously, and he wandered far and wide, and it became a real problem to track him. During the collared period, Galge male raided crops on a number of occasions.
Hamine (the yellow coloured range) is a female that was collared outside the Park. She spent the dry season outside the Park and moved into Yala in the wet season. She or any of her herd never raided crops. Her herd, which was called the Thambarawa group, numbered around 24 animals, but Hamine was most often seen with her calf and another female with a similar aged calf.
Elephants are wild animals and can be very dangerous. In Sri Lanka approximately 60 people die annually from conflict with elephants. Subsequent to the tracking study, one of the team members G.V. Gunawardene, met an untimely death during the course of his work for the DWLC, by an elephant he was attempting to rescue from a well it had fallen into.
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