Old World Scavenger

When we think of vultures, maybe an arid savannah comes to mind with the ugly creatures hovering high above, waiting for the opportune moment to descend and feast on a carcass.  To us vultures are just scavengers, and their very presence is associated with death, but the Cinereous vulture plays an important role in its ecosystem and does so with some amazing adaptations.  Cinereous Vultures or Aegypius monachus are the largest birds in the Old-World vulture classification, Old-World meaning vultures that inhabit the continents of Europe, Asia, or Africa.  Hence its Old-World moniker, the Cinereous vulture inhabits a range across Europe and Asia that stretches from Spain to China during the breeding season.  During the winter the vulture will range from the Middle East, across India, and as far East as the Koreas.  Amazingly, different groups of the Cinereous vultures’ have different migratory habits.  Some groups will not migrate whereas others will travel long distances between their breeding and winter grounds.  Cinereous vultures are easily identifiable by the bare skin on their neck and head which is often blue-grey in color with some brown down feathers surrounding the neck resembling a monk’s hood.  The large body is covered with dark brown feathers making the bird appear even larger than its already daunting 2-3 ft. standing height and its 9 ½ ft. wingspan.  Weighing in at approximately 13-30 lbs., this vulture resembles a small plane more than a bird as it soars high above the ground in the upper levels of the troposphere.  A few adaptations that I will highlight in this post make this vulture one of a kind and a truly amazing animal worthy of our respect and admiration.

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Range of the Cinereous vulture. http://www.planetofbirds.com/accipitriformes

The Cinereous vulture, like other vultures, is a scavenger.  It feeds primarily on carrion (the decaying flesh of dead animals), but Cinereous vultures have been observed killing small or sick animals such as rabbits or tortoises.  Unlike other vultures, the Cinereous vulture is not fond of company , it prefers small groups or pairs as it searches for food.  They use their talons to hold the carcass and their beak to tear flesh away from the bone, but you may be wondering how they hold down rotting meat.  One of the incredible adaptations the Cinereous vulture is the contents of its stomach, which allow it to eat rotting meat.  The pH levels in a vulture’s stomach can be as low as 0 or 1, the highly acidic contents break down rotten or disease ridden meat quickly killing off pathogens before they can infect the vulture.  The stomach contents of the Cinereous vulture do more than simply help it break down a meal, the vulture can also use it as a defense.  If threatened, the vulture can induce vomiting creating a horrible stench that would drive most predators off, and at the same time it lightens the bird allowing for a faster escape.  If the predator gets to close when the vulture is vomiting, the highly acidic stomach contents can burn the predator and whatever else it touches.  Vultures will also defecate directly onto their feet as a way of cleaning themselves.  The waste not only cools their legs, but it also contains enough acid to sanitize the legs of the sick/rotten animal remains they have been standing in while feeding.

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Cinereous vulture (right) feeding with Griffon vulture (left). http://www.arkive.org/cinereous-vulture

Cinereous vultures are monogamous, once they find a mate they will mate for life.  Once they reach 5 or 6 years of age the vulture will find its mating pair and begin to construct their large nest.  Although it is currently unknown how the vultures go about selecting a mate, once a mate has been selected, the vultures will begin to build a nest together.  Nests are composed of sticks, branches, trash, and pine needles, and the nests can reach sizes up to 8 ft. wide and 7 ft. deep.  The nests are usually found high in the trees or on the ledges of cliff faces.  The nests are reused as the vulture pair continue to add to the nest every year they return to mate in that location.  Once they mate, a single egg is laid and under proper conditions a chick will hatch in 50-55 days.  The parents will take turns incubating the egg and once the chick hatches, one parent will stay with the chick as the other searches for food.  The food brought back by the parent is then regurgitated so the chick can eat.  The chick will be able to leave the nest once it is fully fledged around 100-120 days after hatching.

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Cinereous vulture feeding a chick in the nest.  http://www.arkive.org

Flying in the upper levels of the troposphere, the Cinereous vulture has two especially helpful adaptations that allow it to find prey from such a great distance, and venture to heights not many organisms could survive at.  The Cinereous vulture spends much of its time flying at an elevation anywhere from 30 ft. to 6,500 ft., but incredibly the vulture has been seen on Mount Everest at altitudes of 23,000 ft. or 4 miles high.  Cruising at such great heights, the Cinereous vulture needs extremely keen eyesight if it hopes to locate carrion far below.  Unlike many New World vultures that use their keen sense of smell. Cinereous vultures rely on their well-developed eyesight and have a relatively poor sense of smell in comparison.

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Cinereous vulture flying high above, scanning the ground for its next meal.  http://hotspotbirding.com 

Another special adaptation that allows the vulture to cruise effortlessly miles above the rest of us is their specialized hemoglobin.  Hemoglobin is a protein molecule found in red blood cells that binds four oxygen molecules it picks up in the lungs and transports the oxygen to the rest of the body; returning carbon dioxide to the lungs to be exhaled.  Cinereous vultures possess a specialized hemoglobin that allows it to absorb more oxygen at greater heights.  Whereas most organisms would succumb to hypoxia (a deficiency of oxygen in the tissues) at these elevations.  The hemoglobin alpha-D subunit found in this vulture has such a high oxygen affinity that it allows the Cinereous vulture to respire normally even with the low partial pressure in the upper troposphere.  Vultures possess multiple iso-hemoglobin differentiations in which their red blood cells contain four separate alpha-chain iso-hemoglobins with graded oxygen binding affinities.  To state in simpler terms, the hemoglobin of the Cinereous Vulture contains alpha-D chains of hemoglobin (grabs more oxygen than regular hemoglobin) and alpha-A chains of hemoglobin (ensures efficient oxygen delivery to cells of respiring tissues) that work in tandem to allow the bird to respire normally at high altitudes.

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This graph shows how an increase in altitude correlates to a decrease in the percentage of oxygen in the air, highlighting the importance of the vulture’s specialized hemoglobin. http://www.high-altittude-medicine.com

These amazing creatures are unfortunately decreasing in numbers yearly and are listed as Near Threatened by the IUCN Red List of Threatened Species.  The two main threats that plague the Cinereous vulture are human interaction and a lack of available food sources.  Poisoned bait traps have hurt the vulture population as they find, eat, and in some cases feed their chick the poison before it kills them.  In Mongolia, the vultures follow the nomads and eat the livestock that have died.  The practice of giving livestock antibiotics has increased and any livestock that die will be eaten by the vultures; by eating the carcass, the vultures ingest the antibiotics which have been shown to increase chick mortality rates.  Humans will also hunt them, and destroy their nests which also has been detrimental to their numbers.  While the overall population is decreasing (currently 14,000-20,000 mature individuals), some hope remains in Spain and France.  A large population of Cinereous vultures live in Spain (about 2,000 individuals) and their numbers are continuing to increase.  In France the Cinereous vulture has been reintroduced with the preliminary findings being positive.  Hopefully, strongholds of the Cinereous vulture will continue to reappear throughout its range as conservation efforts such as decreasing the use of poison traps increase.  Until then, if a trip to the Old Country is not possible, you can view two beautiful Cinereous vultures at the Lincoln Park Zoo in Chicago.

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Photograph of a Cinereous vulture at the Lincoln Park Zoo taken by myself. http://www.lpzoo.org
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