Persecuted fruit bat may be key to Durian’s survival in Asia

The fruit bat has been persecuted due to the belief it destroyed crops of Durian. Now critically endangered, it seems that it is a key pollinator for the fruit tree.
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Durian has yet to take off as a major fruit in the West. This might be due to the smell, which as been described as “turpentine and onions, garnished with a gym sock“.

Despite this demand is booming for durian. And this means that management of durian orchards is becoming more pressured. Obviously there’s no fruit without pollination and durian has some unusual pollinators. Chiefly it seems to be pollinated by bats, along with spiderhunters (a bird) and giant honey bees. This is due to a rich nectar, which packs 869 calories per millilitre. To get a whole millilitre you’d need to visit just three flowers. That’s quite a food source and it’s not just attractive to cave bats and birds. It also attracts Pteropus hypomelanus, the flying fox, the biggest fruitbat in the world. What happens when a massive bat hits the durian trees? It’s been thought that it’s damage to the flowers, but a team of scientists have been investigating further.

Using camera traps, researchers collected video evidence showing the island flying fox (Pteropus hypomelanus) pollinating durian flowers, leading to the production of healthy durian fruit. Their study – Pollination by the locally endangered island flying fox (Pteropus hypomelanus) enhances fruit production of the economically important durian (Durio zibethinus) – has been published in the Journal of Ecology and Evolution.

Island flying fox (Pteropus hypomelanus) feeding on durian nectar. Source: Aziz et al. (2017)
The video footage was captured on Tioman Island by a team led by Dr Sheema Abdul Aziz as part of her PhD. Dr Sheema said: “These are very important findings because they shed more light on the crucial ecosystem services provided by flying foxes. Previously it was known that the smaller, nectar-feeding bats are pollinators for durian – but many people believed that flying foxes were too large and destructive to play such a role. Our study shows the exact opposite: that these giant fruit bats are actually very effective in pollinating durian trees.” The team was able to show this because there was vertical stratification in the feeding niches of flying foxes and nectar bats, with flying foxes feeding at greater heights in the trees.

Spatial patterns of animal interactions between durian flowers along a vertical gradient
Spatial patterns of animal interactions between durian flowers along a vertical gradient between 6 and 20 May 2015. Nectar bat (Eonycteris spelaea), flying fox (Pteropus hypomelanus), and plantain squirrel (Callosciurus notatus) detections were amassed from 1,528 10-s video clips. Giant honeybee (Apis dorsata), moth (Lepidoptera), and unknown insect detections were amassed from 948 camera-trap photographs. Red dotted lines indicate heights at which cameras were deployed. Source: Aziz et al. (2017)

This is critically important news for durian farmers as the island flying fox is already classified as ‘endangered’ on Malaysia’s National Red List.

Large fruit bats of the genus Pteropus are severely threatened by hunting and deforestation. They are often sold and eaten as exotic meat due to an unsubstantiated belief that consuming them can help cure asthma and other respiratory problems. They are also persecuted and killed as agricultural pests, as some people claim that the bats cause damage and economic loss by feeding on cultivated fruits.

Consequently, these factors have led to a severe decline in flying fox populations worldwide. This could be a problem for tropical plants in fragmented habitats, such as durian plantations isolated by deforestation.

Dr Ahimsa Campos-Arceiz, one of the coauthors of the study, said: “The durian is a fascinating plant that, with its flowers pollinated by bats and its seeds dispersed by large animals like elephants, beautifully exemplifies the importance of plant animal interactions. The durian fruit is particularly famous for its pungent smell and unique taste, adored by most people in Southeast Asia and so often misunderstood – abhorred? – by westerners. We hope this study brings attention to the urgency of conserving flying foxes in Southeast Asia.”

Source: AlphaGalileo

References

Yumoto, T. (2000). Bird-Pollination of Three Durio Species (Bombacaceae) in a Tropical Rainforest in Sarawak, Malaysia. American Journal of Botany, 87(8), 1181. https://doi.org/10.2307/2656655

Aziz, S. A., Clements, G. R., McConkey, K. R., Sritongchuay, T., Pathil, S., Abu Yazid, M. N. H., … Bumrungsri, S. (2017). Pollination by the locally endangered island flying fox (Pteropus hypomelanus) enhances fruit production of the economically important durian (Durio zibethinus). Ecology and Evolution. https://doi.org/10.1002/ece3.3213

Fleming, T. H., Geiselman, C., & Kress, W. J. (2009). The evolution of bat pollination: a phylogenetic perspective. Annals of Botany, 104(6), 1017–1043. https://doi.org/10.1093/aob/mcp197


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3 COMMENTS

  1. This means small-calories, not the kilocalories which is normally given on food when people say ‘calories’. Probably this paper means 0.9 kcalories/ml, 869 (small) calories/ml, about the same as a Starbucks Frappucino. Oil/petrol/gasoline, the most energy dense food, is 9 (kilo)calories per g; sugar is 4 kcalories/g.

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