Study finds smaller skull measurements in Madagascar’s flying foxes

What you need to know

• The researchers examined cranial and dental measurements from 121 museum specimens. The collection spans more than 150 years, allowing the team to compare measurements across time. 1
• Several adult cranial measurements declined directionally, with the clearest change beginning around 1980. The study also reports a significant decline in a combined measure of cranial variation over the past century. 12
• The researchers link the timing of the change to the expansion of commercial hunting, but this association does not show that hunting caused it. Climate change, deforestation and shifts in fruit seasons are also raised as possible contributors. 13
• The measurements do not demonstrate that hunters selectively removed the largest bats. Dental results were mixed: most measured dental traits declined, while one increased, and the changes were less consistent than those in cranial measurements. 123
• The species is hunted for food, and low reproductive output, continued hunting and habitat loss are identified as concerns for long-term population viability. Possible effects on seed dispersal and forest regeneration remain concerns, not outcomes measured in this study. 123

Why this matters

The Malagasy flying fox is discussed as a seed disperser, so changes to the species could matter beyond the bats themselves. However, this study does not show that the measured cranial changes have altered seed dispersal, reproduction or population viability. 23

What happens next

The central questions are whether hunting can be separated from climate, habitat and food-season effects, and whether the measured changes affect bats in the wild. Further work would also need to establish how well museum specimens represent Madagascar’s regions, collection periods and local hunting pressures. 13

What we know

• The study used 121 museum specimens collected over more than 150 years. 1
• It reports declining cranial measurements over time, with the clearest shift around the period when commercial hunting expanded. 123
• The IUCN page supplied for the species lists it as Vulnerable with a decreasing population trend, but its displayed assessment dates from 2014 and is not a recent reassessment. 4

What we don't know

• Whether hunting caused the cranial changes, or how much other pressures such as climate, habitat loss or seasonal food changes contributed. 13
• Whether the pattern reflects heritable change, a shift in the ages of animals represented, or a combination of factors. 13
• Whether the measured changes affect survival, reproduction, population viability or seed dispersal in the wild. 23
• How representative the museum specimens are across Madagascar, different collection periods and local hunting pressures. 13

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