Vulture Awareness Day – The Importance of Vultures in the Ecosystem
Vultures across the world are a vital part of their respective ecosystems, but they face persecution and various threats. Lizzie discusses why these scavengers are important, and what is being done to help them…
Illustration by Eva Kunzova.
There are 23 extant species of vulture and condor, with over half of these are currently classified as threatened, endangered, or critically endangered. Vultures can be classified into two groups; the new world vultures (Cathertidae – residing in North and South America), and the old world vultures (Accipitridae – residing in Europe, Africa, and Asia).
So, what is a vulture?
Most vultures (except the palm nut vulture, Gypohierax angolensis) are carnivorous. Vultures have been identified as the only obligate scavengers with most relying solely on carrion as their food source, rather than hunting their own prey. Although both vulture families occupy the same ecological niche (how the species interacts with their environment and other species within it), they are only distantly related, with new world vultures descended from storks, and old world vultures descended from birds of prey.
However, as both families occupy a similar niche in their environments, they have independently evolved to have similar characteristics through a process called convergent evolution. Most vultures have large, broad wings, with cinerous vulture (Aegypius monachus) wingspans reaching up to 3m! These are designed for soaring and riding thermals which helps birds preserve energy when looking for food. Another key adaptation of vultures is a large crop (pouch of skin in the throat) which helps them consume more meat at each carcass, sometimes to the point where they are too heavy to fly. This is an adaptation to their feed-or-famine diet style, sometimes going days or weeks without feeding. However, the most recognisable feature of vultures is a lack of feathers on the head and neck, preventing any matting that would occur while feeding on carcasses (apart from the bearded vulture, Gypaetus barbatus, which has primarily evolved to eat bones).
Why are vultures important?
The feeding style of vultures can be separated into three main categories; “gulpers” that eat soft tissue, “rippers” that tear off tough tissue, and “scrappers” that pick on smaller pieces of meat. This variation in eating styles and the presence of multiple species at a carcass can mean that vultures are incredibly efficient at consuming carrion and have been seen to strip a carcass in as little as an hour. For this reason, vultures are commonly referred to as “nature’s clean-up crew” and are estimated to dispose of up to 70% of Africa’s carrion, and more meat than all other predators combined in Central and South America. Combined with a well-developed immune system and stomach acid 100 times stronger than humans’, vultures are able to consume rotting and infected carcasses without being ill. This incredible ability has been shown to prevent the spread of diseases including TB, anthrax, and rabies.
The efficiency of vultures as carrion-eaters means that facultative scavengers (animals that only scavenge some of the time) have to rely on less ‘easy’ food sources, hunting their own prey. This competition for food sources ensures that populations of facultative carnivores are kept in check. Declines in vultures can result in huge population booms of these predators and massive upheaval in the food web as this results in huge population declines in prey species. Vulture population declines in India were shown to result in feral dog populations increasing by up to seven million individuals, leading to increased interactions between feral dog packs as well as with humans and domestic dogs. This increased interaction has since been highlighted as a key cause of the rabies outbreak of 1992-2006 which killed an estimated 48,000 people. Scientists stress the importance of learning from this decline and using it as a ‘window to the future’ to understand and predict the effects of future declines elsewhere.
“Without vultures, reeking carcasses would likely linger longer, insect populations would boom, and diseases would spread – to people, livestock, and other wild animals” – National Geographic
However, the benefits of vultures to humans are not limited to health and sanitation. Relationships between vultures and humans in Yemen were shown to be mutualistic with higher densities of vultures in areas with human activity and vultures disposing of up to 22.4% of organic waste in towns and cities. A study of vultures in Spain quantified this benefit over a year and found that vultures’ ability to rapidly consume livestock carcasses was estimated to reduce CO2 emissions by 77,344 tons by minimising the transport of carcasses in vehicles and save $50 million in insurance costs. Vultures also provide religious benefits to communities that use “sky burials” (a funeral practice where the deceased are left on the mountain to be consumed by scavengers). Vulture declines in India left the Parsi people struggling to continue this practice and resulted in a massive crisis in the faith and reduction in followers.
What are vultures threatened by?
A 2004 study examined extinction risks of all bird families globally and found both families of vultures to be among the most threatened. 17 years on, many vulture species are still threatened, with 11 of the 16 old world species at risk of extinction within the next 50 years. For both families, poisoning through exposure to lead, pesticides, and veterinary medicines are highlighted as the main threats with poisoning events occurring even in protected areas and killing up to 500 individuals in a single event. A study focussing on new world vultures found that 100% of the assessed individuals showed evidence of long-term lead exposure from multiple sources. Lead contamination is highlighted as a threat wherever vultures are found, and is shown to cause catastrophic declines in some species. In fact, lead fragments in gut piles left by hunters were a main cause of the California condor decline resulting in just 22 individuals in 1982.
More recently, the veterinary anti-inflammatory drug diclofenac was identified as the main cause of vulture declines in India, however, due to the efforts of international campaigns, this drug was banned in India and Nepal in 2006. Currently, the main geographical concern is vultures in sub-Saharan Africa where poisoned carcasses are intentionally left for carnivores such as African lions (Panthera leo) and black-backed jackals (Lupulella mesomelas). These carcasses lead to direct poisoning of vultures as well as poisoning of multiple other scavengers which then die and are scavenged by vultures. This poisoning causes cascades through the ecosystem, leading vultures to suffer the most casualties. A study of African vultures assessed eight species and found that seven had declines over 80% over the past three generations, with poisoning and trade for traditional medicines accounting for 90% of reported deaths. Alongside poisonings for bushmeat and by poachers to avoid vultures alerting rangers, these threats mean that some populations are becoming at risk of extinction and increased conservation efforts are vital for saving these important scavengers.
How can we conserve vultures?
It’s not all doom and gloom! In fact, there are some incredible conservation efforts happening to conserve these critical species. Perhaps the most famous vulture conservation effort is captive breeding and rewilding, with the most iconic example of this being the California Condor (Gymnogyps californianus). In 1982, only 22 condors remained in the wild and the difficult decision was made to bring the remaining birds into captivity. Over almost 40 years, these birds have been carefully bred to maintain genetic diversity but it was slow going with pairs only producing one egg per year. Today, however, there are 504 individuals, with 329 now flying in the wild, perhaps one of the most successful conservation efforts in history. This technique has since been used for a range of species with over 300 bearded vultures now inhabiting the Alps after their extinction in 1913 and new vulture breeding centres, coupled with vulture restaurants (feeding stations providing poison-free carcasses of known source) supporting populations in India and Nepal.
Now, more conservation projects are looking to the future, rather than focussing on repopulating historical ranges, with multi-species action plans promoting international collaborations across migration routes and vultures being considered in planning for infrastructure. However, more research is needed to effectively conserve these birds as currently, little is known about how disruptions of social habitats may contribute to declines and impede recovery. Scientists highlight the need to focus on how population declines may inhibit information sharing - as individuals in flight scan wide distances and head towards areas where other individuals are descending to a possible carcass - and how this could be combined with research into carrion diversity to highlight key areas for vulture restaurants. Organisations such as VulPro are now trying to fill these gaps by focussing on all aspects of vulture conservation, combining research into wild and captive populations, practical conservation and rehabilitation, and educating local communities to inspire the conservationists of the future. Because when we fight for vultures, we fight for the whole ecosystem, including ourselves.
“Vulture conservation work not only protects these ecologically important birds but as umbrella species, these efforts also benefit their habitat and other wildlife such as other endangered raptors as well as large herbivores.” – Vulture Conservation Foundation
Thank you to Eva Kunzova for her beautiful illustration. You can find more of her work on her Instagram @evakunzova.illustration
Lizzie Upson
Lizzie is an MSc Biodiversity and Conservation graduate from the University of Exeter based in Yorkshire. She is particularly interested in ecology as well as the power of volunteering in conservation and environmental change. Lizzie is currently working on a few publications assessing population change in birds and is looking for more Citizen Science projects to build her experience.