Part 1 – The Amboseli Context: Ecology, People, and Genetics

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Chapter 2 – Amboseli Ecosystem Context: Past and Present

Chapter 2, Amboseli Ecosystem Context: Past and Present (Harvey Croze and W. Keith Lindsay), lays out the physical and ecological features of the Amboseli landscape. Variability and unpredictability are the hallmarks of semi-arid ecosystems that impose huge demands for resilience and adaptability on the resident plants and animals.

A vital feature of the Amboseli ecosystem is a series of five major swamps fed perennially from the sub-surface drainage of Kilimanjaro in Tanzania immediately to the south of Amboseli National Park. The swamps, and the grasslands and woodlands along their margins, support a remarkable array of large mammals (which the chapter catalogues briefly). Only two of the swamps are protected by the national park. The rest are under dire threat of permanent alienation from uncontrolled development.

Facts:

  • Average Amboseli rainfall is only 340 mm (13 in) and highly variable from year to year. A Dry Season Intensity index shows there were 6 serious drought years and 11 relatively good years between 1972 and 2002.
  • Amboseli National Park, the protected core of the elephants’ range, at 390 km2 (150 mi2) is only 5% of the Amboseli ecosystem, as defined by the annual ranges of the large mammal community.
  • The Amboseli basin, an ancient Pleistocene lake bed, is 1,100 m (3,600 ft) above sea level. The 5,892 m (19,330 ft) peak of Kilimanjaro, the tallest free-standing mountain in the world, is 40 km (25 mi) to the south.
  • The elephants’ total range (8,000 km2, 3,000 mi2) stretches more than 30 km (ca. 20 mi) across the international boundary into northern Tanzania.
  • The elephant population has grown from 600-800 in 1972 to over 1,500 in 2010, ca. 3% annual increase. (It is now ca. 1,350 due to recent drought and poaching mortality.)

Amboseli is a ‘non-equilibrium’ ecosystem, in which there is no steady state and no prescribed target numbers corresponding to classical temperate zone ‘carrying capacity’. Ecologists now know that the numbers, proportions and distribution of the plant and animal components of most ecosystems are in constant change, morphing over time and space from one state to another.

The chapter concludes with an example of such a non-equilibrium shift in Amboseli. Over the years the face of Amboseli changes aperiodically from more-woodland-less-swamp to more-swamp-less-woodland. Change is the name of the game, and that is what the elephants and other wildlife (and wildlife managers!) have to cope with.

Chapter 3 – The Human Context of the Amboseli Elephants

Chapter 3, The Human Context of the Amboseli Elephants (Kadzo Kangwana and Christine Browne-Nuñez), describes the complex mosaic of human settlement and land use that surrounds and in many places insinuates into the elephant’s daily range and life. [Full summary text to follow.]

Chapter 4 – The Population Genetics of the Amboseli and Kilimanjaro Elephants

Chapter 4, The Population Genetics of the Amboseli and Kilimanjaro Elephants (Elizabeth A. Archie, Courtney L. Fitzpatrick, Cynthia J. Moss, and Susan C. Alberts) explores the evolutionary history of the elephants living in the Amboseli ecosystem. It uses the analytical tools from population genetics, an area of biology that infers evolutionary processes from patterns of genetic diversity in populations.

We first review how elephant behavior—especially mate choice and dispersal patterns—shape the structure of genetic diversity in elephant populations. We then explore the genetic connections between the elephants in Amboseli and Kilimanjaro, and the genetic history of these populations in the context of other elephant populations across Africa.

Almost all genetic information on the Amboseli and Kilimanjaro elephants was discovered using DNA extracted from elephant dung. This method is ideal because dung can easily be collected without disturbing the elephants. But it presents methodological challenges in collectioning and genotyping, which we explain in a special section (Box 4.1).

Facts:

  • Poaching causes many females to lose their relatives, sometimes forcing them to form new families with non-kin.
  • The founding genetic matrilines (lines of female decent) in Amboseli occur in several other elephant populations across Africa, suggesting that elephants in the past were wide-ranging, with high levels of movement between populations. For example, the Kilimanjaro elephants have one matriline that so far is only also found in Kruger National Park, South Africa.
  • The Amboseli and Kilimanjaro elephants are not genetically distinct: they share some founding genetic matrilines and are members of one continuous population.

In sum, the Amboseli elephants represent one of the most genetically intact populations in Africa, where females are still able to live together with their maternal relatives in families and bond groups.

Poaching and habitat fragmentation are increasingly disrupting the behavior and genetic structure of wild elephants. Conservation efforts must focus on maintaining corridors for movement between populations.

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