Monday, August 26, 2013

Massive Migration

     Elephants are the largest land mammals on earth, and big animals need lots of space.  We know that elephants migrate annually to find food and water, and that the matriarchs lead their herds from year to year (learn more by reading previous entries in our blog!).  However, the full migratory paths of both Asian and African elephants is neither well studied nor well known.  There are a number of challenges in studying these routes, from overcoming technological hurdles to combating bureaucratic red tape.

Many elephants need many resources.  Photo by Rebecca Shoer

      Elephants require large migratory  ranges for a number of reasons.  Most obviously, they consume huge amounts of food every day, and must move when an area's resources are depleted.  In addition, female and male elephants have almost entirely separate social lives, and migrate independently of one another (and thus their migratory routes rarely overlap).  Male elephants may travel alone or in loose bachelor herds, but obviously must return to a female herd to mate.  What is the typical range for an elephant, then?  It seems to vary over subpopulations of elephants, but some estimates have been made, especially in India:

Home  ranges of over 600 km² have been recorded for females in south India (Baskaran et al., 1995). In north India, female home ranges of 184–326 km² and male home ranges of 188–407 km² have been recorded (Williams, 2002). Smaller home range sizes, 30–160 km² for females and 53–345 km² for males, have been recorded in Sri Lanka (Fernando et al., 2005).
(IUCN Red List)
     However, such estimates are few and far between, and most research has been done in few select areas of Asia.   Why is this? First of all, Asian elephants live in a mixed habitat of grassland and jungle, making them quite difficult to locate and track in the wild.  Some African elephants have been micro-chipped or radio collared so that they might be tracked, but these devices are both expensive to purchase and require a veterinarian to install safely.   Second, as elephants have such large home ranges, they inevitably cross human-created borders, either between states or countries.  This creates a challenge for both the migrating elephants and the researchers attempting to track them.  In 1999 "The Old Elephant Route" project was started in the Patkai Range, along the border of India and Myanmar (Burma) to assess the range and activity use of this known migratory corridor (Chowta et al).  Unfortunately, the project suffered constant setbacks due to the political situation in Myanmar.  Although they were eventually able to gather enough data through India to map the migration patterns of some elephants, they still had to struggle both with hauling equipment in the wilderness and recruiting volunteers during a time of political turmoil.

Modified from the Aane Mane Foundation

     Finally, the major obstacle in studying elephant migration is the tremendous level of habitat loss that has occurred and is still occurring in southeast Asia.  Even if elephants still attempt to follow their traditional migration routes, they have to traverse over farmland, through villages, and across roads.  In northern India, a highway was constructed in 2009 that directly cut through a four mile wide known migratory corridor (Novak, 2009).  This corridor served as the only route by which the roughly 1,000 elephants residing in that region could access a critical water source.  In Thailand, only 15% of the natural forest still remains, and the 3,000 wild elephants that still live in the country are isolated in national parks.  Even if we were able to track their migration routes, such routes have most likely been so altered due to human influence that the elephants no longer traverse the large areas they once did.  However, in countries like India where both large wild elephant populations and large natural areas still exist, it is critical that we identify where these elephants travel in order to protect those areas from human development.  It is not enough to protect areas that elephants may be in today, or tomorrow, but the entire area that an elephant may use in an entire year.  Unfortunately, this is rapidly becoming a remote possibility in southeast Asia, as the human population continues to increase.  The urgency of the elephant's situation cannot be overstated.

Novak, Sara. 2009. "The Plight of the Asian Elephant--New Highway Checkpoint Threatens to Cut Off Elephant Life Line."
Chowta, P. 2010. "The Old Elephant Route."  Aane Mane Foundation.

Choudhury, A., Lahiri Choudhury, D.K., Desai, A., Duckworth, J.W., Easa, P.S., Johnsingh, A.J.T., Fernando, P., Hedges, S., Gunawardena, M., Kurt, F., Karanth, U., Lister, A., Menon, V., Riddle, H., Rübel, A. & Wikramanayake, E. (IUCN SSC Asian Elephant Specialist Group) 2008. Elephas maximus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. <>. 

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