Masai Mara – scavenging raptors

We spent six days wandering the Mara triangle in the Masai Mara National Reserve in early November. One of the aspects I was interested in was seeing how the predators were coping after the main migration had passed through the area about two months earlier.

“One day your life will flash before your eyes. Make sure its is worth watching.” ~ Gerard Way

The bulk of the migration passes through this area between August and October but there is a stream of wildebeest and zebra which are still journeying through the south eastern end of the Mara triangle in November. This means there is still plenty of food for the predators who are bound by their territorial imperative.

“It is not the strongest of the species that survives, nor the most intelligent. It is the one that is most adaptable to change.” ~ Charles Darwin

Where there are predators there are bound to be kills and where there are kills you are likely to find raptors. Not all raptors are primarily hunters, but many will scavenge when the opportunity presents itself and some are obligatory scavengers.

Many raptors like the Martial, Crowned and Fish eagles are primarily hunters as are Hawk eagles, Snake-eagles, Harrier-hawks, Goshawks and falcons. Others are opportunitist like harriers, buzzards and kestrels which will hunt or scavenge based on the available opportunities.

“The measure of intelligence is the ability to change.” ~ Albert Einstein

One hunter and opportunist is the Secretary bird. It has the head of a raptor but the physique of a crane. This raptor is primarily a terrestrial being which can often be seen striding, in pairs, through the open grasslands looking for prey. The Secretary bird will fly if pushed, but prefers to walk through the grasslands.

This raptor has a open skinned face which is a red-orange and its intensity depends on how excited it is, much like a Bateleur or Harrier-hawk. The Secretary bird hunts and catches prey on the ground, often stomping on its victim to kill it. Secretary birds can also be seen stomping on grass tussocks to flush out food. When caught and sufficiently stomped on, the prey is usually swallowed whole and often alive. The Secretary bird feeds on anything from snakes and other reptiles to young gamebirds, and from amphibians to tortoises and rats, and any other small mammals they can catch.

Most raptors are purely hunters but some eagles, such as Steppe and Tawny eagles and Bateleurs, although primarily hunters, also scavenge. While travelling down a valley alongside the Myvumba Nane hill to find a pride of lion we saw this young Bateleur sitting in the shade of a sausage tree along a lugga.

Young Bateleurs are brown in colour with white dappling. They have greenish, blue-grey facial skin. It can take a young Bateleur 7 to 8 years to transform from its brownish colouring into striking adulthood colours of black, white and chestnut brown.

The adult Bateleur has a red face and feet. Bateleur eagles can change the colour of their faces and feet depending on their mood. The blood vessels are very close to the surface and they can control blood flow to these vessels. A mature Bateleur’s face can be an orange-yellow when it is relaxed and turn into a bright red-orange colour when it is excited or agitated. The Bateleur’s red feet are also unique because they have shorter toes and thicker scales on the tops of their feet compared to other birds of prey. These adaptations help protect them from the bites of venomous snakes, their favorite food in the wild.

Unusual for raptors, mature Bateleur males and females are physically very different from each other — something known as “sexual dimorphism”. Both sexes are mainly black with a rusty chestnut back and ashy grey wing coverts, but females also have grey secondaries with a trailing black edge. This makes it very easy to differentiate males from females, whether they are perched or in flight. I do not know if it is possible to differentiate the sex of an immature Bateleur.

While some eagles both hunt and scavenge, vultures are obligate scavengers. Vultures are classified into two groups: old world vultures, found in Africa, Asia and Europe, and new world vultures, found in the Americas. These two groups are not genetically related but have developed similar biological traits, such as their method of scavenging.

“I am still learning.” ~ Michaelangelo

Most raptors hunt for their prey and prefer hunting alone, but vultures are rough, cooperative scavengers. One of the key reasons they do not hunt is that they have relatively weak legs and feet and are not able to carry away their prey.

Vultures scavenge, but to scavenge they need to find a carcass. They do this by flying to great heights in the sky and scan large areas of the ground below for signs of a kill or carrion. Vultures are skilled soarers and gliders but are too heavy to be overall good flyers so they rely on thermals to lift them to the heights needed for long distance travel and high altitude surveillance. With the rising warm air pockets they are able to soar over distances up to 150kms.

“We cannot direct the wind, but we can adjust the sails.” ~ Dolly Parton

Africa is home to 11 “old world” vulture species, the largest of which is the Lappet-faced. This an impressive raptor due to its huge size and aggressive behaviour.

Old World vultures do not have a good sense of smell so they rely mainly on incredible eyesight to locate food. A soaring vulture is estimated to be able to spot a one metre animal carcass from up to six kilomteres away, suggesting that their vision is eight times better than that of a human.

The lappet-faced vulture can have a wing span up to 2.9 metres. This old world vulture has perfect adaptations for a scavenging life. Its powerful hooked bill cuts easily into a carcass’ skin and tendons, and its bare head and neck reduce lengthy feather-cleaning after it has pushed its head deep into a messy carcass.

The Lappet-faced vulture prefers open savannah areas with scattered trees, so you will not find them in forested areas. The next image shows a Lappet-faced vulture grabbing a Ruppell’s griffon vulture which has a small piece of bone and sinew in its beak.

Even if other vultures have arrived at a carcass first, most are not able to cut into the hide of a carcass if it has not be opened up by other predators. A Lappet-faced vulture is powerful enough to tear open a carcass with its massive beak and because of this is often the first at an untouched carcass. The aggression of a Lappet-faced vulture is directed toward other vultures and even Black-backed jackals. It is big enough to take on all of them.

A Hooded vulture flying in to join the feeding fenzy on the left overs of a zebra killed by lions the previous night. The Hooded vulture is the smallest of the African vultures. It is usually seen on the fringes of a vulture-covered carcass. It is too small to mix it up with the White-backed and Ruppell’s Griffon vulture, so it eats scraps dropped by the other vultures and Black-backed jackals.

Ruppell’s Griffon vulture is also a very large raptor standing up to one metre high and having a 2.5 metre wingspan. Males and females have similar colouration — brown or black feathers with a white edge. The underbelly is white flecked with brown. It has a white fluffy collar and its neck and head are essentially bare. Its eyes are usually amber to yellow in colour. This vulture has a large powerful beak with a pinkish tinge to it.

“The two most powerful warriors are patience and time.” ~ Leo Tolstoy

The Ruppell’s Griffon vulture is thought to be the highest flying vulture and has been known to reach heights of 36,000 feet. It clearly must have some temperature and oxygen adaptations to be able to stay at these exceptional heights.

Scavenging birds play a vital role in our ecosystems. They clean up carcasses before they have time to rot. Without scavengers, rotting carcasses would become hubs for harmful pathogens. Vultures specialise in eating carrion and are highly efficient at cleaning up a carcass. The African White-backed vulture is the most common African vulture species in much of sub-Saharan Africa. The next image shows a White-backed vulture with full flaps down in final approach to a crowded kill site.

A kill site attracts a macabre group of scavengers from opportunist eagles to an assortment of vultures, storks, jackals and hyaenas. This carcass even attracts a Marabou stork. This is a massive bird towering over vultures and eagles. The Marabou eats mainly carrion, scraps, and faeces but will opportunistically eat almost any animal matter it can swallow, including nestlings, fish, frogs, eggs, lizards and even crocodile eggs if it can find them. The next images shows a Ruppell’s Griffon vulture tugging at a bone that a Marabou stork had picked up.

Scientists believe that the White-backed Vulture, like most other vultures, often rely on other vultures and scavengers such as jackals and hyenas, to locate food. The White-backed vulture will look out for concentrations of other vultures or watch the movements of terrestrial scavenging animals. Once a carcass is located, the vultures descend to the ground and will wait in trees or on the ground nearby for long periods of time if the carcass is occupied by large predators. Once the large predators, like lions and hyaenas move off, the vultures descend on the remains to feed. There appears to be a pecking order in the vulture mayhem around a carcass dictated by size, strength and aggression.

Researchers have found that these scavengers are laden with flesh-degrading Fusobacteria and poisonous Clostridia. As bacteria decompose a dead body, they excrete toxic chemicals that make the carcass a dangerous meal for most animals. Interestingly, vultures often wait for decay to set in, giving them easy access to dead animals once the tough skins have partly decomposed. Vultures have developed an extremely tough digestive system, which destroys the majority of the dangerous bacteria they ingest. They also have a tolerance toward some of the deadly bacteria that would kill other animals and these bacteria seem to flourish in the vulture lower intestine.

Different vulture species have different-shaped beaks, which means that each feeds on a particular part of a carcass (like innards, muscle tissue or hide). This adaptation reduces competition for food. While the Lappet-faced, Ruppell’s Grffon and White-backed vultures are usually in the thick of it, the smaller hooded vultures, which do not have the same physique and powerful beak, tend to hang around the fringe of the vulturine feeding frenzy waiting for scraps to be dropped amid all the squabbling.

When Lappet-faced vultures arrive and they normal come in pairs, they do not wait to be asked to the dinner table. They have a imposing approach.

Unlike many raptors, vultures are relatively social and often feed, fly or roost in large flocks. A group of vultures is called a committee, venue or volt. In flight, a flock of vultures is a kettle, and when these raptors are feeding together at a carcass, the group is called a wake.

“Knowing is not enough we must apply. Willing is not enough we must do.” ~ Bruce Lee

Seven of Africa’s vulture species are on the edge of extinction. With the demise of vultures comes a problem on an economic and social scale as yet uncalculated, and certainly unrealised. Vultures provide a vital ecological service benefiting humankind. They are nature’s scavengers – clearing up carcasses and waste that would otherwise rot and spread disease. Source: Birdlife International.

The more we value things the less we value ourselves.” ~ Bruce Lee

Explore, seek to understand, marvel at its inter-connectedness and let it be.

Have fun, Mike

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