SpOTTED HYENAs ARE - Leibniz Institute for Zoo and Wildlife

The Spotted Hyena Project
is a long-term research project on the spotted hyenas
of the Serengeti ecosystem from the Leibniz Institute
for Zoo and Wildlife Research in Berlin, Germany. It
was initiated in 1987 in the Serengeti National Park
and since 1996 we also study the population in the
Ngorongoro Crater.
Our main research topics:
• the social behaviour and the evolution of key traits
of spotted hyenas
• the ecology and population dynamics of spotted
hyenas in the Serengeti and Ngorongoro Crater
• the epidemiology of pathogens and their impact on
individuals and populations
• the impact of hyenas on ecology and population dynamics of their main prey and competitors
• the impact of humans on spotted hyenas and other
wildlife species
Our research is based on detailed observations of
behaviours and interactions, long-term demographic
data, and samples collected non-invasively from several thousand individuals. We recognise the hyenas by
their individual spot patterns, scars, ear notches and
their personality.
compiled BY
Dr Oliver Höner & Dr Bettina Wachter
Leibniz Institute for Zoo and Wildlife Research
Alfred-Kowalke-Str. 17
D-10315 Berlin
Germany
[email protected]
[email protected]
Spotted hyenas
in the
Ngorongoro Crater
Their life in a complex society and their
role in one of the world’s most
fascinating ecosystems
Spotted Hyena Project
P.O. Box 40
Ngorongoro, Arusha
Tanzania
[email protected]
Dr Victor Runyoro
Ngorongoro Conservation Area Authority
P.O. Box 1
Ngorongoro
Tanzania
[email protected]
Copyright 2009
Photographs © Oliver Höner & Bettina Wachter
Design and layout © Steven Seet
For more detailed information about spotted hyenas
and our project or our institute please visit our website
at:
www.izw-berlin.de/flink/hyenas.htm
Donations are welcome !
Spotted hyenas
are ...
important
They are by far the most abundant large
carnivores in African savannas.
They keep the savannas healthy by
hunting weak, old and diseased prey
and consuming dead animals.
fascinating
They live in groups of up to 80 members that are dominated by females.
They express highly complex social behaviours similar to those of primates.
Females usually give birth to 1 or 2
cubs and invest more in their young
than any other African carnivore.
successful
They have survived for hundreds of
thousands of years despite fierce competition with bigger cats such as the
sabretooth and lion.
Leibniz Institute for Zoo
and Wildlife Research
Spotted hyena groups consist of up to 30 adult
females, 20 adult males, and their young. In these
‘clans’, there is a strict
Society
x
A Comple
linear dominance
hierarchy in which all
females (and their young) dominate all males. Each
clan is thus led by an ‘alpha female’, followed by her
young and all other females. Below the lowest ranking
female comes the ‘alpha-male’, followed by all other
males.
Young of both sexes obtain a social rank immediately below that of their mother because the mother
supports them during interactions with other clan
members. Daughters then remain in their birth clan
throughout their lives and build close bonds with their
mother and sisters. This system of coalitions usually
is stable for many years, but sometimes a coalition
of lower-ranking females manages to overthrow the
Ngorongoro Conservation
Area Authority
Spotted hyena mothers nurse their young for up to 2
years with milk that has the highest protein and one
of the highest energy
Excellent Mothers and fat contents of all
land-living carnivores. And their investment pays off: hyena cubs stand
a higher chance to survive to adulthood than young of
most other carnivores.
Females usually give birth in a den away from the
communal den to ensure mother-cub familiarisation.
When the cubs are about 2 weeks old, the mother carries them to the communal den.
alpha-female coalition.
Males usually disperse to another clan when about 3
years of age, thus most adult males in a clan are immigrants. They join the hierarchy of the new clan at
the very bottom, and because males rarely fight, they
normally increase in rank only when higher-ranking
males die or leave the clan. As a result it takes a male
many years to reach the top of the male ‘queue’.
The structure of dens permits access only to cubs. This
protects them against attacks by lions or other hyenas
when their mothers are away.
Females give birth at any time of year and all females
of the clan reproduce. They have their first litter when
they are between 2 and 5 years old. Because daughters
of high-ranking females get more milk and food, they
have their first litter at a younger age than daughters
of low-ranking females.
Spotted hyena cubs are, in contrast to young from
all other carnivores, born with their eyes open and
teeth fully erupt. Twins start
twin Rivalry competing with each other for
access to the mother’s teats and
milk immediately after birth, and during the following 7 weeks, they sort out who will be the dominant.
They can be quite aggressive to each other during this
period, because the social rank is very important in
a hyena’s life, and rank order among twins does not
normally change after this initial period.
In the Serengeti, prey abundance in a clan’s territory can be very low for long periods. Mothers then
regularly travel to the migratory herds of wildebeest to
feed. When the herds are far away and mothers return
to the den only after several days, competition for milk
between twins increases and may lead to starvation of
the subordinate.
In contrast, in the Crater, there is always prey nearby
and mothers nurse their cubs at regular, short intervals. As a result, aggression between twins usually is
very low and we have never observed cubs starving due
to sibling rivalry.
Spotted hyenas live in a ‘fission-fusion’ society. This
means that clan members do not always stay together,
but frequently forage
Communication and rest alone or in small
groups. When two clan
members meet, they go through a ritualised greeting
ceremony: they stand parallel and face in opposite
directions, lift one hind leg and sniff each other. The
unique aspect of these greetings is the prominent role
of the erect (pseudo-)penis which is used to signal
submission.
Their highly social nature has led to the evolution of a
wide variety of vocalisations. Probably best known is
the ‘whoop’, which can be heard over several kilometres. Spotted hyenas whoop to recruit other clan members to defend the territory, communal den, and food
resources, and to display their status to other hyenas.
Hyenas often also ‘laugh’ or ‘giggle’, but against common belief, they do not use these calls when they are
happy but when they are highly stressed and signal
their submission to a more dominant hyena.
They also use scent to communicate. Their scent glands
are situated between the tail and the anus. During
scent-marking a greasy secretion is deposited from a
semi-crouched position over a grass stalk or small bush.
The scent is individually distinct and has a clan odour.
In spotted hyenas, fetuses of both sexes are exposed
to high levels of androgens, hormones that are considered male sexual
Females are special ! hormones because
they trigger the
formation of the male sexual organs. This and a genetic
predisposition cause females to develop outer sexual
organs that resemble those of males: they lack a vaginal
opening and have a penis-like clitoris through which
they copulate and give birth. Due to the narrow birth
channel, first-time breeders often have stillbirths.
Because females have control over mating, they can
choose their mates. Genetic paternity analyses have
shown that females prefer
Choosy Females sires that behave in a
‘friendly’ manner rather
than males that harass them or try and monopolise
them. Males therefore invest a lot of time in developing
friendly relationships with females.
According to evolutionary theory, a structure with
such high costs should be selected against unless it
has benefits that outweigh the costs. One important
benefit is that the pseudo-penis gives females control
over mating because a male needs the full cooperation
of the female during mating. Choosing a good mate is
very important for females because they invest so much
in their young.
As adults, female hyenas have androgen levels that are
similar to those of other mammals, including humans,
and much lower than those of males. Female dominance over males therefore is a result of males being
non-aggressive and submissive to females rather than
females being particularly aggressive.
Spotted hyenas are very skilled and powerful hunters.
In the Crater, they mostly hunt wildebeest, but they are
also able to overcome
Diet and Foraging prey as large as adult
buffaloes. They hunt
solitarily or in small groups, running at moderate
speed into a herd to select an individual and then chase
it over long distances at speeds of up to 60 km/h until
it is exhausted.
The hyenas in the Crater hunt most of their food
themselves, but they also scavenge animals that died of
disease (an important task!) and the remains of kills of
other carnivores. Despite their abundance and hunting
abilities, they do not regulate the population size of
their prey but instead the hyena population is regulated by the abundance of their main prey in the Crater.
Crater hyenas compete with lions for kills almost every
day. When groups of lions consist of females and their
young, the
Competition with Lions hyenas often
manage to
recruit a sufficiently large number of clan members to
keep their kills or drive the lions off. However, when
adult male lions are present, lions always dominate
their kills or take over kills from hyenas, no matter
how many hyenas are present. Against common belief,
it is usually the lions that steal kills from hyenas rather
than vice versa.
Females also prefer males that have joined their clan
after they were born. This is a simple but effective way
for females to avoid incestuous breeding with their
father or older brothers. Because young females prefer
newcomers, most males select clans with many young
females when they start their reproductive career.
The Crater floor is currently inhabited by 380 hyenas
in 8 clans. Clans contain between 30 and 80 members
that defend territories of
Territoriality 30 km2. In ecosystems
with fewer prey than in the
Crater such as the Kalahari in Botswana, hyena clans
are smaller and territories can be as large as 1000 km2.
Clans defend their territories through vocal displays,
scent marking, boundary patrols and during encounters with hyenas from neighbouring clans.
Although clan territories are marked and defended, hyenas in the Crater regularly undertake excursions into
territories of other clans to feed. The size of a hyena
clan therefore is not limited by the abundance of prey
inside the clan’s territory.
Territory owners cannot completely prevent other
hyenas from intruding into their territory, because it
would be energetically too costly to keep all potential
intruders out. They have, however, priority of access
to food, water and resting places within their clan’s
territory.