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The spotted hyena

Crocuta crocuta


A Spotted Hyena
A Spotted Hyena
The spotted hyena or laughing hyena has the scientific name Crocuta crocuta, which comes from the words crocus (meaning saffron coloured) and utus (which means provided with). They are the largest members of the hyena family that evolved from ancient relatives of the civet in Eurasia about 10 million years ago. They are dog-like in appearance with spotted coats and bushy tails. However, they are more closely related to civets, cats and genets. They can grow to be around 1.9m in length and weigh as much as 86 kg.


Taxonomy:

Level
Classification
Kingdom
Animalia
Phylum
Chordata
Class
Mammalia
Order
Carnivora
Family
Hyaenidae
Genus
Crocuta
Species
Crocuta

Habitat
africa.png
Figure 1: Spotted Hyena Habitat (Red)


The spotted hyena is native to Africa and can be found in Botswana,
Burkina Faso, Cameroon, Central African Republic, Congo, Ivory Coast, Kenya, Mali, Mozambique, Namibia, Nigeria, Senegal, Sierra Leone, South Africa, Sudan, Tanzania, Zambia, Zimbabwe and throughout sub-Saharan Africa.
Of all the large carnivores in Africa, they hold the highest population.

They have adapted to many diverse habitats such as deserts, dense and dry woodland, forests on mountains as high as 4000m altitude, marshes, semi-desert habitat and swamps. The Namid Desert is known to house many spotted hyenas along the seasonal rivers. Population density varies, but they often have denser populations than other large carnivores (lions, brown hyenas, striped hyenas etc.) In their primary habitats, such as the Aberdare Mountains in Kenya, Ngorongoro Crater of Tanzania and the Serengeti ecosystem.

Hyena territories can vary from 30 square kilometres to more that 800 square kilometres. Less pressure from neighbouring clans and larger availability of food and prey contribute to larger hyena territories. The range of these territories frequently overlap with those of brown hyenas and striped hyenas. There used to be many such territories in south Africa, but most have been turned into built up areas by humans.
Top Left: Open Grassland, Top Right: Forest, Bottom Left: Desert, Bottom Right: Swampland
Top Left: Open Grassland, Top Right: Forest, Bottom Left: Desert, Bottom Right: Swampland
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Adaptations


The Spotted Hyenas' adaptations help them survive in the environment that they live in.

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Structural Adaptation One:

One of the structural adaptations the spotted hyena has developed is its powerful jaws. Spotted hyenas have evolved to sport larger teeth, especially large premolars and carnassials (see Diagram 2) than most other carnivorous mammals in order to stop their teeth from wearing out too quickly. Their sharp carnassials, which can be used for slicing hide and tendons, are positioned behind their premolars to minimise damage when crushing bones. This is what caused them to become primarily pack hunters (only scavenging about 7% of the time), as their teeth allow them to cling on to live prey and rip them to shreds.

They also have big jaw muscles and a vaulting around their skulls, which adds to their strong bite strength of 4500 newtons. With this amount of jaw power, they are able to carry their prey or parts of their prey around, as well as dine on virtually all parts of their prey including the bone without waiting for their prey to die. In fact, they can live purely on almost all bones except large elephant bones. An experiment conducted in 1955 found that a group of spotted hyenas only took 3-4 minutes to fracture and chew up a cow vertebra. It is believed that the spotted hyena developed their jaw strength in order to improve their ability to survive during times of famine.

Structural Adaptation Two:


Pressure from neighbouring rivals is one of the reasons for why spotted hyenas sport two scent glands each. They are used for marking territories by rubbing two scent glands located near the anal opening against grass stalks. This produces a strong smelling soapy white paste that will tell other animals about the individual that owns the territory. Often, the individual will also scratch the floor with their front paws to lay down scents from their interdigital glands.

Their scent glands are practical tools for securing food and prey within the territory from other predators like lions, as well as protecting individual hyenas and cubs near dens. Scent marking also discourages opposing hyena clans from intruding, thus preventing battles which may lead to casualties.

Behavioural Adaptation One:


Spotted hyenas are nocturnal, so reduced visual abilities during nighttime have led to their flourished range of vocalisations. They have around 20 different calls which are vital to communicating within their social structure. For example, the whooping sound that travels over several kilometers can be used as an effective assembly call in cases were food or territory need defending. It can also be used to locate individuals or to recruit team members for hunting.

Their most distinct call is their high-pitched, demented laugh, which is mostly produced by subordinates to signal frustration over being chased or attacked by higher ranked hyenas that want to hog the food. It's also very loud and can carry over 4.5 kilometers. This means that the laughter may potentially draw other hyenas or other larger predators, encouraging the more dominant spotted hyenas to share their food supply in order to keep their subordinates quiet.

Behavioural Adaptation Two:


In response to increased competition from other carnivores, spotted hyenas became involved in social behaviours that maximized cooperation within clans. This would in turn increase the effectiveness of clan operations, such as dining, hunting and mating.

To maintain social bonds, Hyenas hold greeting ceremonies after periods of separation during hunts. Longer periods of separation often mean more elaborate ceremonies. These ceremonies include thorough and lengthy inspections of each other's genitals via sniffing and licking. Lower ranked individuals of both sexes will maintain erections as a sign of submission and volunteer themselves for inspection first by lifting one of their legs. Hyenas of higher social status are less likely to hold erections. These ceremonies are crucial in reestablishing social roles and relationships and help restrict aggression within clans.

Physiological Adaptation:


Alpha females give their babies higher levels of androgen - a male sex hormone that boosts aggression during the final months of pregnancy. This encourages young males to practice mounting females early and frequently in order to improve their chances of passing on their genes when mating in the future.
The extra doses of androgen often causes cubs of the same sex to attack each other viciously, killing off up to 25% off all cubs to ensure the survival of the fittest. This aggressiveness gives individuals a better chance at getting a meal when they live in groups of up to 90 members that will fight over food. This is especially true for pregnant or lactating females, who are often the most aggressive feeders because they need to secure enough energy to produce nutrition for their young.

Bibliography:


Cavendish, Marshall. Exploring Mammals . Volume 3. Paddyfield, 2008. 644-658. Print.

McHan, Ashley. et al. "Hyena." In the Savannah. N.p., 2001. Web. 28 Jul 2010. <http://library.thinkquest.org/J0113249/hyena.htm>.

"Spotted Hyaena: physical description." Welcome to the IUCN Hyaena Specialist Group website. IUCN Hyaena Specialist Group, 2010. Web. 28 Jul 2010. <http://www.hyaenidae.org/the-hyaenidae/spotted-hyena-crocuta-crocuta/crocuta-physical-description.html>.

Carey, Bjorn. " The Painful Realities of Hyena Sex." Live Science. TechMediaNetwork.com , 26 April 2006. Web. 28 Jul 2010. <http://www.livescience.com/animals/060426_hyena_cubs.html>.


"What's To Love: Hyena's Lifestyle." Animal Planet Videos. Web. 28 Jul 2010. <http://animal.discovery.com/videos/whats-to-love-hyenas-lifestyle.html>.