Neglected Mammal and Bird Pollinators in the Spotlight

Mammal and bird pollinators, hitherto neglected groups compared to the more extensively-scrutinised insect pollinators, face serious threats in India, according to new research, which is a comprehensive analysis of species richness and extinction risk of birds and mammal pollinators in India and reveals both their hotspots and threats they face.

Mammal pollinator hotspots are restricted to the south of the Western Ghats which includes places such as Kollam and Pathanamthitta in Kerala and Kanyakumari in Tamil Nadu, while bird pollinator diversity is scattered across the country, the study reveals. An analysis of the hotspots of threatened vertebrate pollinator species — based on the IUCN Red List of conservation status of plants, animals and other organisms — shows that only mammal pollinators such as certain bats, monkeys and squirrels are currently classified as threatened in India. The study found multiple hotspots of population declines for birds and mammal pollinators mainly in the south of Western Ghats.

The study identifies 85 birds and mammal species, which is about five percent of the total population of the bird and mammal species in India, as pollinators. This includes some widely-found bat species such as the Indian flying fox or Pteropus giganteus, the greater short-nosed fruit bat or Cynopterus sphinx, and Leschenault’s rousett or Rousettus leschenaultii.

Threat to pollinators

Most pollinators appear to be threatened by human activities such as agriculture, logging and hunting for food and medicinal purposes, the study notes. Such risks to pollinators have ecological and economic implications such as reduced food production, plant extinction, loss of functional and genetic diversity, and economic damage. Scientists could not find evidence of specific genetic traits in these species for being responsible for their declining numbers.

“We suggest protection of vertebrate pollinators should be emphasised in active conservation agendas in India,” the scientists note in the paper.

Researchers mapped biodiversity hotspots and regions where pollinators were most threatened, which, according to Sheena Cotter from the school of environmental sciences at the University of Lincoln, UK and one of the authors of the study, are “vital information for governments to inform policy planning”.

One of the key messages from the study is the importance of bats as vital, economically important pollinators, says Cotter. This is significant as the bat population in India is on the decline due to lack of adequate protection.

The scientists found many fruit-bat species as key pollinators and seed-dispersers of several economically and medicinally important plant species, including durian in northeast India. Of the 13 fruit-bat species of India, all but Latidens salimalii or Salim Ali’s fruit-bat, considered one of the three rarest bats in the world, are listed as pests or vermin under the Indian Wildlife Protection Act 1972, says Cotter’s colleague Ratheesh Kallivalapil.

Many mammal pollinator species such as the Indian giant squirrel Ratufa indica and the jungle palm squirrel Funambulus tristriatus in India are endemic to the Western Ghats. Unsustainable habitat destruction and harvesting are believed to cause their extinction locally across the region. Bats and primate pollinators are particularly vulnerable due to their low reproductive rate, mostly one pup per litter every year, and high age of maturity, which reduces their quick population recovery, he says.

Pollinator-friendly conservation

The team of scientists observed several gaps in the distribution of pollinators, indicating habitat fragmentations with ecological implications such as reduced food source for pollinators, low-quality pollen transfer between plants, plant genetic diversity reduction, and local extinction of both pollinators and plants.

The study highlights the importance of implementing pollinator-friendly conservation methods, such as establishing pollinator corridors between the fragmented landscapes, planting pollinator-friendly plants at the edge of agricultural lands, roadsides, or common paths or parks, says Kallivalapil. “This type of conservation methods we can see across the UK and other parts of Europe. However, this is not yet implemented or practised in India despite having vast agricultural lands.”

“This study is the first comprehensive analysis of the macroecological patterns of species richness and the risk of extinction of bird and mammal pollinators in India,” says Kelvin Peh, associate professor of conservation science at the University of Southampton, who led a global assessment of the importance of vertebrate pollinators for plant reproductive success. “Prior research has focused primarily on insect pollinators, making this study significant in filling the knowledge gap on vertebrate pollinators,” he informs Mongabay-India.

Conservation outcomes

The study reinforces some recent global reports on the decline of vertebrate pollinator species. For instance, the global assessment of the importance of vertebrate pollinators says that, given the potential for substantial negative impacts associated with the loss of vertebrate pollinators, “there is a clear need for prompt, effective conservation action for threatened flower-visiting vertebrate species.”

The assessment, which is based on a meta-analysis of 126 experiments on animal-pollinated plants, shows that there is an average of 83% reduction in fruit and seed production when bats are excluded, and a 46% reduction when birds are excluded.

The study highlights “the need for prompt conservation actions for these crucial pollinators due to their significant impact on ecosystems and agriculture,” says Peh and adds that additional research on how such changes might affect wider ecosystems is required.

Kallivalapil suggests a review of the existing (conservation) policies to list all fruit-bats in the protected schedules (I or II). “The existing policies should be amended to categorise them in the protected status; promote nectar and plant corridors in agricultural landscapes through incentives to farmers; promote their conservation and awareness among the communities; and promote pollinator-friendly plants and nest box installation in gardens and parks,” he adds.

Neglected pollinators

Vertebrate pollinators are typically ignored in studies examining the importance of pollinators in general, probably because they are a much less important group in the global north, which dominates the scientific arena, explains Cotter.

Historically, pollination research has focused on insects because they are the most common pollinators, often perceived as the primary pollinators for most flowering plants, leading to a bias in research priorities, agrees Peh.

This perception has been reinforced by their significant role in agricultural pollination, which has direct economic implications.

In contrast, vertebrates are very important in the sub-tropics, where they pollinate a wide diversity of ecologically and economically important plants. Vertebrate pollinators such as birds and bats are also typically more widely dispersed and mobile and hence, require large areas of land to be protected.

Cotter observes that the importance of vertebrate pollinators in the sub-tropics is not matched by the scientific study or understanding of their conservation status and distribution. “Most vertebrate pollinators’ distribution spans across economically poor African and Asian countries, many of which often struggle with basic research facilities, funding, expertise, and interest and fieldwork support,” adds Kallivalapil.

“We need to promote interdisciplinary research by encouraging collaborations between environmental economists, ecologists, conservationists, and policy-makers to develop comprehensive strategies for the conservation of vertebrate pollinators and their pollination services,” Peh recommends. “We also need to establish long-term monitoring programmes to track vertebrate pollinator populations and their impacts on their pollination services.”

This story was first published on Mongabay India