Summary

Over the past century, like in other African countries, the African wild dog (Lycaon pictus) population in Zimbabwe has declined.

 In particular in Hwange National Park, an area that used to harbour a viable population, a sharp decline in the population has been documented. One of the main reasons for this decline is that over the years African wild dog packs either moved closer to or into the buffer zone along the northern boundary of the National Park. Within the buffer zone African wild dogs get increasingly exposed to human activity resulting in mortality, this is also known as an ‘edge effect’. The mortality rate is so high that it exceeds natality and ultimately there is no recruitment and packs fall apart in groups far below their optimal pack size necessary for successful reproduction.

When animals show a preferential choice for sink habitat they are said to have been caught in an ecological trap. Habitat choice behaviour is beneficial in classic source-sink systems, as animals living in high quality habitat (natality>mortality) only choose to migrate into low quality habitat (natality<mortality) when there is not enough high quality habitat available. Within an ecological trap habitat choice is detrimental and can lead to rapid extirpation of a species, as animals living in high quality habitat choose to migrate into low quality habitat even when there is enough high quality habitat available. Ecological traps occur when sudden natural or human induced changes cause formerly reliable settlement cues to be no longer associated with an adaptive outcome, causing animals to make a maladaptive habitat choice. To be able to distinguish a sink from an ecological trap additional knowledge of the relationship between habitat preference and habitat quality is required.

Within the Hwange system African wild dogs seem to base their habitat choice on the right fitness enhancing ecological cues.

 They experience a higher hunting efficiency in the buffer zone outside Hwange National Park, less competition with lions (Panthera leo) and spotted hyenas (Crocuta crocuta) and a better access to suitable den sites. As a result African wild dogs outside the National Park give birth to larger litters of pups. However, due to an ‘edge effect’, human induced mortality in the buffer zone is so high it exceeds natality. African wild dogs nevertheless make a maladaptive habitat choice and move into the mortality sink outside the safety of the protected area as they are unable to judge habitat quality accurately by taking this human induced mortality risk into account. In other words, African wild dogs in the Hwange system are caught in an ecological trap in the buffer zone outside Hwange National Park. Within an ecological trap, habitat choice is detrimental and likely to result in a rapid collapse of the system and extirpation of the species involved. The fast decline in the African wild dog population in and around Hwange National Park supports the finding that the Hwange system serves as an ecological trap. In order to ensure a fast recovery of the population it is recommended to expand conservation efforts beyond the borders of the protected area and focus on countering the human induced mortality in the buffer zone surrounding Hwange National Park.