Mopane worms are widely harvested as a food source in Southern Africa. Containing three times more protein than beef or chicken, as well as more calcium, iron and zinc, and less fat than conventional livestock, they are often fried or boiled and eaten as a snack or a meal. 

Although mopane worms play an important role in local livelihoods, culture and the environment in mopane woodlands, little is known about their genetic diversity or how their populations are distributed across different regions. Considering reports of overharvesting in Botswana, Namibia, South Africa and Zimbabwe, we must gather this information to help ensure the species’ long-term sustainability.

This is according to researchers at Stellenbosch University (SU), the South African National Biodiversity Institute, the Botswana International University of Science & Technology and the Ongava Research Centre in Namibia.

They analysed the DNA of mopane worms in Namibia and the Limpopo River Basin (South Africa and Botswana) to understand their genetic diversity and how populations have spread and changed over time. They collected adult moths and caterpillars from different trees and at different stages in South Africa, Botswana and Namibia.

The findings of their study* were published recently in the journal Conservation Genetics.

“We offer the first look at how mopane worm populations are related and distributed across Namibia and the Limpopo River Basin, and how their numbers have changed over time. Genetic data can help guide wildlife conservation by showing how different populations are related, how big they are and how they move or connect with one another,” says lead author Dr Barbara van Asch from the Department of Genetics at SU.

She adds that identifying areas with high genetic diversity is important as this information can help guide conservation efforts, local policies and how resources are allocated.

“This genetic data is crucial for planning effective conservation strategies as concerns about the species’ sustainability have grown over the past two decades due to rising demand, habitat loss, climate change and a dramatic increase in cross-border trade between Botswana, South Africa and Zimbabwe worth millions of dollars.” 

According to Van Asch, the mopane worms they studied show clear genetic differences across long distances, and populations from Namibia and the Limpopo River Basin don’t share the same maternal lineages.

She notes that in both Namibia and Botswana, mopane worm populations are genetically similar, with little variation between areas that are fairly close to each other – 51 to 160 km apart in Namibia and 19 to 78 km apart in Botswana. Mopane worms collected in South Africa have the highest genetic diversity and genetic differentiation. 

“Strikingly, half of the sampling areas had only one unique genetic ‘fingerprint’ or pattern in their DNA. The fact that these sampling sites all have the same genetic ‘fingerprint’ suggests that the genetic diversity is very low across the Limpopo River basin to the west of Musina. Worms from the southernmost sampling areas have the highest genetic diversity and can be potential candidates for targeted conservation. These sampling areas are not located within protected areas. 

“In Namibia, mopane worms show less genetic variation between different areas. In Botswana, they have the lowest genetic diversity of all the regions studied. Genetic evidence suggests that mopane worm populations in Namibia have expanded over time, while those in South Africa and Botswana have remained stable.

“Nonetheless, the low genetic diversity in mopane worm populations, especially in Botswana, suggests there are fewer variants, which could limit their ability to adapt to environmental changes.”

Van Asch says their results suggest that mopane worm populations in South Africa and Botswana may need conservation support, such as moving individuals from healthier populations to help restore those that have become weaker. More importantly, it is crucial to protect mopane woodlands from the rapid destruction now taking place. 

According to her, information about the genetic diversity of mopane worms or their distribution across different regions is valuable because the absence of formal, standardised record-keeping and consistent monitoring makes it very difficult to trace harvesting activities. 

“A significant portion of harvesting activities remains undocumented. Because mopane worms are harvested widely and without proper controls or monitoring, the practice may have become unsustainable, making the species more vulnerable to extinction.” 

Van Asch says they hope to expand their analyses to more populations in the Limpopo River Basin, Zimbabwe and Zambia, where mopane worms are also commercially harvested.

• Source: Nethavhani, Z et al. 2025. Multimarker genetic analyses of Gonimbrasia belina, the most harvested wild edible insect of mopane woodlands in Southern Africa, support concerns over the sustainability of the species. Conservation Genetics. DOI: 10.1007/s10592-025-01687-1

*The study was conducted by Zwannda Nethavhani (Stellenbosch University), Ruan Veldtman (South African National Biodiversity Institute/Stellenbosch University), Casper Nyamukondiwa (Botswana International University of Science & Technology), William Versfeld (Ongava Research Centre) and Barbara van Asch (Stellenbosch University).