Relocating female tigers could help boost small populations and their genetic diversity

Tigers are threatened by habitat loss and fragmentation, reducing and isolating key populations, particularly in Southeast Asia. Tigers need large habitats to survive, and the recent isolation of many small populations can decrease genetic diversity, potentially compromising their persistence and resilience. In similar species, this has manifested through reduced fertility levels and offspring survival, as well as increased vulnerability to disease and the impacts of climate change.

A new study led by Dr Eric Ash, of the Department of Biology's Wildlife Conservation Research Unit, looked at these crucial factors in the context of theoretical tiger translocations in Thailand’s Dong Phayayen-Khao Yai (DPKY) forest complex. The DPKY is currently a key refuge for the Indochinese tiger (Panthera tigris corbetti) – one of the most endangered subspecies, now thought to number only around 200 individuals living in Myanmar and Thailand. The forest complex supports a small, isolated breeding population of approximately 30 individuals.

Infographic with illustrated male and female tigers, with the caption: Translocation of females consistently resulted in higher population numbers and genetic richness than translocation of males

Image: Sarah Markes / WildCRU

Relocating individuals from other areas is one technique conservationists use to help sustain or re-establish isolated and vulnerable populations. Many variables influence the success of such initiatives, in terms of both overall population growth and genetic diversity.

The researchers evaluated the potential effect of translocations on the Indochinese tigers in DPKY by simulating over 20 generations (around 100 years), based on the population’s current state. They then compared the impact that tiger translocations from a related population could have on the trajectory of the population and its genetic diversity. Exploring variations in the number, frequency, and sex of individuals translocated, they found that translocation of females consistently resulted in higher population numbers and genetic richness compared to translocations of males. However, genetic diversity was shown to decline markedly over time unless additional individuals were introduced at regular intervals. The findings suggest that adding four females every generation or alternate generation (5-10 years) would be ideal.

This work provides important insight into the potential trajectory of the tiger population in DPKY, and more broadly illustrates the crucial importance of monitoring and managing genetic inheritance in small populations of endangered species.

Wildlife populations around the world are experiencing habitat loss and fragmentation, presenting a threat to many species. Tigers and other large carnivores are particularly vulnerable, with potential cascading impacts on the broader ecosystem arising from their decline. A key challenge that conservationists are facing is understanding how best to manage small, isolated populations to maintain genetic diversity; this study provides novel insight not only for tiger management and population modelling, but also for other large carnivores facing similar threats.

To read more about this research, published in Scientific Reports, visit: