The irreplaceable roles of crocodiles and their relatives risk being lost

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ZSL press release.

As the risk of crocodilian extinction increases, these well-known species aren’t the only thing we stand to lose. New research in the Journal of the British Ecological Society Functional ecology points out that the unique roles these reptiles fulfill in their respective ecosystems are also under threat.

A Gharial Crocodillian creating a ‘raft’ for their young. Credit: Phoebe Griffith.

According to new research conducted by the ZSL (Zoological Society of London).

Up to 38% of the various ecological functions that crocodilian species provide to wider ecosystems are at risk of being lost, researchers say in an unpublished study.

Published in Functional Ecology, the study identifies the crocodile, alligator, caiman and gharial species most in need of conservation action. They each play important, yet different and diverse roles in the ecosystems they live in, leading the authors to call for greater conservation protection for these highly endangered species, based on their unique ecologies.

If we lose these species, we risk losing the important roles they play, forever.

The study examines the diversity of ecological roles of crocodilians by looking at measurable characteristics related to how the species function in their environment, such as skull shape, body size, and habitat use. Researchers have developed a database of these key characteristics for all species, revealing often surprising ecological functions performed by crocodilians.

From the prolific burial of the critically endangered Chinese alligator (扬子鳄; Alligator sinensis)-which provides vital shelter and refuge for other species-to control agricultural pests as in the case of the Philippine crocodile (Crocodylus mindorensis, locally known as Buwaya), which eats the invasive apple snail; crocodilians are vital engineers of the ecosystems in which they live. Some, like the largest crocodile in the world, the Saltwater Crocodile (porous crocodylus), travel hundreds of kilometers across the open ocean, traversing critical terrestrial, freshwater, and marine habitats, transporting nutrients between ecosystems.

The miniature Chinese alligator digs complex burrow systems and can endure some of the coldest winters of any crocodile species. Credit: James Hennessy, National Reptile Zoo.

More than half of all crocodilians are threatened with extinction due to habitat loss, hunting, bycatch in fishing gear and damming of rivers. The loss of these endangered species would mean that we would lose the various ecological roles they perform, with unknown and potentially devastating ecological consequences.

Many of the crocodiles we highlight as ecologically distinctive are also species threatened with immediate extinction.

The researchers, hailing from ZSL’s Institute of Zoology (IOZ) and the EDGE of Existence programme, the University of Oxford’s Wildlife Conservation Research Unit and the Gharial Ecology Project in India have discovered that some species have particularly unique ecologies, such as the critically endangered species. gharial (Gavialis gangeticus). The gharial is an aquatic species specially adapted to life in water with a long and narrow snout ideal for catching fish, its main prey. Its presence is indicative of clean and healthy water systems.

Phoebe Griffith, ZSL PhD student and lead author, said: “A lot of people think crocodilians are big predators, catching zebras in wildlife documentaries – but that’s just a small part of the story. Single-Species Behavior There are about twenty-eight species of crocodilians, and they have evolved to be surprisingly different from each other.

“Quantifying the various ecological roles of these species is an important factor in understanding and conserving global biodiversity and in assessing the magnitude of what we stand to lose if these key players disappear.”

“If we lose these species, we risk forever losing the important role they play. We are just beginning to study what these roles are, but some species may be lost before we have had a chance to understand their place in the ecosystems where they are found. This is particularly concerning because many of the crocodiles we highlight as ecologically distinctive are also species in immediate danger of extinction.

Conservation of crocodiles in the Philippines British Ecological Society
Brown and his colleagues discovered this Philippine crocodile eating invasive apple snails, an agricultural pest in the Philippines. Credit: Joseph Brown.

Of the ten species with the most unique ecological functions, six are critically endangered and are so depleted that they are considered functionally extinct in most of their historic range. The two most endangered species – the gharial and the Chinese alligator – are also very evolutionarily unique and highlighted by ZSL’s EDGE of Existence program as EDGE priority species (Evolutionarily Distinct and Global Endangered). The study found that conserving threatened crocodilians on the basis of their evolutionary uniqueness would also have a positive impact on conserving the functional diversity of the species globally.

EDGE postdoctoral researcher Dr Rikki Gumbs said: “From miniature burrowing alligators to giant saltwater crocodiles, the vast evolutionary journey of crocodilians has produced a dazzling variety of shapes, sizes and behaviors. Sadly, many of the world’s most unique crocodilians are in decline and, along with the functions they serve in their ecosystems, are on the verge of being lost forever.

“However, our research shows that we can save much of the diversity we risk losing by prioritizing the most unique species for conservation action. Interestingly, we can also effectively protect endangered crocodilian functions by aiming to conserve their evolutionary history. Essentially, by looking to the distant past, we can effectively conserve crocodilian diversity, and the benefits that this diversity provides to ecosystems, into the future.

ZSL has been working since 2017 to conserve the gharial, the most ecologically unique crocodilian, in India and Nepal. With project partners in Nepal, he has radio-tagged over 40 gharials to provide vital information on why this species remains so endangered. In addition to confirming breeding in Bardia National Park, Nepal, ZSL works with local fish-dependent communities to develop sustainable fish ponds, conduct surveys, monitor and protect nesting sites, and map river use. outside the protected area.

People are the key to crocodilian conservation

In India, a recent ZSL-supported EDGE Fellow working with the Gharial Ecology Project studied the seasonal movements and breeding behaviors of wild resident gharial, living on the Chambal River – by far the largest self-sustaining population in India. species on a global scale.

Now working with the gharial in northern India as part of the Gharial Ecology Project, co-author Dr Jeffrey W. Lang said, “People are the key to crocodilian conservation. If we appreciate the presence of these dinosaur relatives, the conservation of the world’s alligators, caimans, crocodiles and gharials will be a priority.

“Studying them and understanding the importance of these aquatic predators, in the places where they still live, is the first necessary step to ultimately conserving not only the most impressive crocodilians, but also their many interesting and diverse lifestyles. Community gatherings and environmental programs in village schools are essential for local awareness and appreciation of all resident wetland species, including crocodilians.

The study also shows that certain traits help reduce a species’ risk of extinction; species that invest heavily in reproduction, that adapt very well to different habitats, or that can tolerate climatic extremes have a better chance of survival. Crocodilians occupy inherently fragile habitats such as freshwater and coastlines that are often under heavy human pressure. Since many species with distinct ecological functions and high risk of extinction are based in and around Asia, the research highlights the continent as a hotspot of threats for them.

Phoebe concluded: “Our study highlights the highly threatened nature of crocodilians and that immediate and stronger conservation action for many of these species is essential if we are to protect their ecological functions in freshwater habitats in which they are. It’s so important that freshwater habitats are among the most threatened on Earth, yet provide many critical services for our planet.

You can read the full research article here:

https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2435.14140

/Public release. This material from the original organization/authors may be ad hoc in nature, edited for clarity, style and length. The views and opinions expressed are those of the author or authors. See in full here.
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