Posts Tagged ‘nilgai’

Tigers (Panthera tigris) Suppress Dhole (Cuon alpinus) Populations.

April 1, 2021

A new study determined tigers suppress dhole pack sizes in India. Dhole packs are smaller in areas with higher densities of tigers, even if there is an higher density of potential prey species. The scientists conducting the study used camera traps to estimate pack size and tiger numbers. In Tadoba-Andhari Tiger Reserve where tiger density is high, there were 7 dhole packs averaging 6.4 dholes per pack. In Navegaon-Naziri Tiger Reserve where tiger density is lower, there were 5 dhole packs averaging 16.8 dogs per pack. Pack sizes were 2.6 times greater in areas with lower tiger density. Both reserves are in a subtropical dry deciduous forest zone dominated by teak, argun, and giant crepe myrtle trees. The terrain is somewhat hilly. Leopards are another important large predator in the reserves, and the leopard population is also negatively impacted by tigers. Common prey species in the reserves include spotted deer, sambar deer, barking deer, nilgai antelope, wild boar, and gaur–a large species of cattle. Dhole pack sizes do increase in areas with greater prey density, but the abundance of tigers is a greater influence on pack size. Dholes tend to prey on smaller animals in areas with lots of tigers, so they can consume more of the animal before a tiger drives them away from the kill. Tigers depress dhole populations by directly hunting them and by chasing packs away from their kills.

Map of tiger reserves where the below referenced study took place. Map from the below referenced study.

Tigers totally dominate dholes. The authors of the study saw tigers kill dholes on 5 different occasions and drive packs away from their kills 23 times. They saw no instances of dholes killing tigers or driving them away from their kills.

Spotted deer are an important prey item for tigers and dholes.
Nilgai antelope, also known as blue buck are another important prey item for tigers and dholes. Hunters introduced nilgai antelope to Texas about 100 years ago, and now there is a feral population of 37,000 in that state.

India has the highest dhole population in the world. There are small packs in the northern montane forest, and larger packs in the dry deciduous forests of central and south India. Since tigers were eliminated from Laos, dhole populations have increased there. Dholes formerly ranged across most of Asia, and during the Pleistocene they ranged into North America, though fossil evidence there is limited to 1 site in Mexico.

Siberian tigers are known to depress wolf populations, and lions depress hyena and hunting dog populations in Africa. I wonder if big cats suppressed canid populations in Pleistocene North America. Saber-tooths were very powerful fanged cats, and American lions grew larger than any big cat species. Pleistocene jaguars grew as large or larger than modern tigers and are at least as common as dire wolves in the fossil record of Florida. There really is no way to know because abundance in the fossil record doesn’t necessarily reflect actual abundance in life.

Reference:

Bhanda, A.; P. Ghaskodbi, P. Nigram, and B. Habib

“Dhole Pack Size Variation: Assessing the Effect of Prey Availability and Apex Predator”

Ecology and Evolution March 29, 2021