Do corridors have the edge?
@ Sri Lanka Nature - 2000
Elephants live in close-knit societies headed by the matriarch, and the typical her comprises interrelated, mature females and their offspring. Young bulls, on reaching adolescence are evicted from the herd, from which time they usually lead nomadic, solitary lives. With the males wondering around and not being permanently attached to a herd, genetic diversity is assured and the risk of inbreeding minimised.
It is now a well-known fact that all elephant herds have their own defined home ranges. Led by the matriarch, they meander around these home ranges in search of food and water. If the conditions are reasonably stable, it is very rarely that the herd wonders out of its home range. However, if the habitat is poor, elephants may abandon their home ranges and go in search of alternate habitats. While the typical home range of a herd is around 160 sq. km, mature males have much larger ranges (up to 400 sq. km).
In Sri Lanka today, due to the poor foresight of successive governments and land-use managers, land has been allocated haphazardly for agriculture and development and not in the context of a carefully considered plan that takes biodiversity conservation into account. Sri Lanka’s forests are now heavily fragmented, and few large areas of contiguous elephant habitat remain. Although herds have become isolated due to this fragmentation, in most cases their home ranges are still adequate, though limited. For the most part, elephants tend to be pocketed within these habitat fragments. However, with the fragments becoming smaller and fewer, it is now becoming increasingly common for herds to have overlapping home ranges. This leads to stress because of competition for food and water; it also increases the pressure on herds to move out in search of new pastures. Thankfully, on-going research indicates that this is not happening yet.
On the other hand, habitat fragmentation is much more disruptive to males who may not be able to access suitable females to mate with without crossing between several fragments. Males often traverse long distances in search of suitable females and find themselves encroaching into villages, farms and settlements. It is here that most of the human-elephant conflict occurs, and this is the reason why, most often, conflict situations involve bulls.
In this scenario therefore, it is prudent to consider inter-linking these pockets of jungle habitat with corridors to allow long-ranging males a chance to cross over to other jungle tracts without coming into conflict with man. These so-called "elephant corridors", linking habitats that otherwise remain separated, become very important in situations like this.
It is important to design the system so that elephants will use the corridor and not "spill over" into surrounding human settlements. The success of a corridor depends on the distance - separating the two segregated areas. If the distances are small then the corridor need not be very broad, but if the distance is relatively large, the corridor has to be much wider. It is estimated that if the corridor is less than 3 km long, it would need to be about a 1 km wide, while one around 10 km or longer should have a width of about 4 km. A corridor should necessarily have a poorer quality of food plants than the habitat fragments it serves to link so as to ensure that elephants use it purely as a corridor and not a home range. The ends of the corridor, especially the areas close to the linking point, should be rich in food vegetation so as to entice the elephants toward the ends.
Corridors are therefore essential tools for elephant conservation and management, particularly when extensive jungle areas are not available for elephant habitats to sustain a viable population. Therefore, in a country like Sri Lanka, where the remaining available elephant habitats are extensively fragmented, properly planned corridors would ensure a viable form of long-term management and continuity of the species, and also serve significantly to reduce human-elephant confrontations.
First mooted at a meeting of the Central Board of Agriculture in 1956, corridors connecting protected areas to allow elephants to undertake long-distance seasonal migrations in relative safety have since been one of the main themes in Sri Lanka’s elephant conservation strategy. The protected areas system in the North-Central Province designed under the Mahaweli Development Scheme attempted to link national parks and sanctuaries with corridors to facilitate elephant migrations. These proposals were indeed visionary at that time and represent pioneer efforts at creating wildlife-dispersal corridors, now much in vogue throughout the world when formulating wildlife conservation and management strategies.
The underlying premise when proposing these corridors is that in Sri Lanka elephants undertake long-distance seasonal migrations between protected areas that can support large elephant populations. But these proposals were based on elephant behavior and ecology research from elsewhere. The presumption was that the patterns and extents of ranging behavior observed in India and even Africa would hold true in Sri Lanka.
But a recent field study implemented in the Southern and North-Central Provinces that used radiotelemetry to look closely and intensely at elephant movements and ranging patterns indicate that unlike in India and Africa, in Sri Lanka elephants do not undertake relatively long-distance migrations. In fact the home ranges of elephants are among the smallest known anywhere — the home ranges of radio-collared animals varied from 50-150 km2, compared to the seasonal home ranges of elephants in India that can exceed 500 km2
The study was also enlightening in other ways. It also indicated that the majority of Sri Lanka’s elephants live outside protected areas; that food in the protected areas is limited during the dry season and elephants move short distances outside of the protected areas in search of food (the extent of the home ranges indicated above include the seasonal movements); and that human-elephant conflicts are largely a result of these dry season forays in search of food.
Thus, the new information indicates that instead of corridors connecting protected areas, an effective elephant conservation strategy should look towards conservation landscapes. We must identify elephant conservation ranges, where large protected areas will provide core protection to elephant herds, but the protected areas should have adequate buffer zones where land-use practices are compatible with conservation goals and minimizes human-elephant conflicts.
An ideal model for such a conservation landscape is the Yala National Park and surrounding areas. The radio-telemetry study indicated that elephants in the national park have adequate food and water during the wet season, but move out of the park and into the immediate ‘buffer zone’ in search of food during the dry season. However the people around the national park still largely practice rain-fed agriculture; therefore, the fields are fallow during this time. Thus, elephants that forage in these fallow fields do not create human-elephant conflicts.
Instead, the dry-season forays can actually be a boon to the people in the buffer zone. The elephant is Sri Lanka’s premier charismatic ‘mega’ vertebrate species, attracting thousands of wildlife enthusiasts to national parks and other areas. Therefore community-based nature-tourism enterprises in the buffer zones can be an economic incentive to the local people to conserve elephants. The revenue from the nature-tourism can also provide compensation for opportunity costs in lieu of dry season crops.
So, the current knowledge of elephant ecology and behavior in Sri Lanka calls for a landscape conservation approach towards elephant conservation where buffer zones rather than corridors are the important feature that adds value to protected areas. But, such a conservation strategy also necessitates a land-use policy in these conservation landscapes that regulates land-use practices and requires careful land-use planning during development in these conservation landscapes.
– Sri Lanka Nature