BEAUTY & NATURE · LIFESTYLE

What to know about Angulate Tortoise; sex and life cycle!!!

Angulate Tortoise

image

Classification:

Phylum
Chordata

Class
Reptilia

Order
Testudines

Family
Testudinidae

Genus
Chersina

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What to know about Angulate Tortoise; sex and life cycle!!!

What to really know they are elongated, single projecting gular scute (throat
shield), which is used in battle to overturn other
male angulate tortoises during mating season.

The angulate tortoise is the only species in the
genus Chersina , and it is endemic to southern
Africa. It has striking markings on its beautiful
shell, which is used for protection.

image

The tortoise
will usually retract its head, feet and tail into the
shell when threatened. Another defence
mechanism is that it will readily eject the liquid
contents of the bowels when handled, often
spraying it some distance. Their adaptability and
hardiness allow them to thrive in captivity, in
which the species has been recorded to live for
up to 32 years.

The angulate tortoise is considered not threatened
and is common and abundant in its home range.

The angulate tortoise is used as a food source by
people living in rural areas of the Karoo and is
also often kept as a pet. Its trade is, however,
closely controlled, because it is listed on CITES
Appendix II and it is a protected species in South
Africa and Namibia.

How to recognise an angulate tortoise
They are the only tortoises on the African
continent with a single throat shield. Males differ
from females in size, shell profile, shell
dimensions, the shape of the supracaudal shield,
tail length, anal notch, and in the presence of a
plastral concavity. Mature males have a carapace
(upper section of the shell) that is elongate and
flared at the front and back. Females have a
pronounced dome and steep sides towards the
rear. The weakly hooked beak is rarely serrated.

They have bent forelegs with five claws on the
front feet and four on each of the back feet.
Buttock tubercles are absent and the tail lacks a
terminal spine. The angulate tortoise has a dark
grey or black shield with a yellow centre around
the dark areola. The marginal shields have
alternating triangles of black or yellow that extend
from the edge of the shell, up the edge of the
costals.

The colour pattern in this species is variable; light
brown and black is the more common pattern.

The plastron (belly) is red-brown with a black
centre. These individuals are found in the Western
Cape and it is this brick-red colour that gives the
species the common name rooipens or “red
belly”.

Getting around
Generally, tortoises are remarkably slow movers.

Over short distances the eyesight of most
tortoises appears to be good.
Communicating
Tortoises are loners, unless it is mating season
when males pursue the females.

Distribution
The angulate tortoise is mainly restricted to the
south-western parts of South Africa, with isolated
recordings of sightings in southwestern Namibia.
Its distribution follows the coastline from
southwestern Namibia, through the Northern and
Western Cape provinces, to the Eastern Cape. A
population of these tortoises is found in the Karoo
National Park, in the Great Karoo. They also occur
on the Robben, Dassen and Dyer islands. They
have probably been introduced to the latter two
islands, but they may have a natural presence on
Robben Island.

Habitat

This species is found in a wide variety of
vegetation types, ranging from sandy coastal
regions and coastal fynbos in the west to mesic
thicket in the east. Isolated, inland populations are
equally at home in
moister habitats with higher rainfall. Both sexes
wander around similar-sized home ranges of up
to 2 ha (often smaller in moister habitats).

Food

Tortoises are herbivorous and their diet includes
grasses, annuals and succulent plants. They do
not have teeth, and with the aid of a horny beak
they shear through grass and succulents. Small
bites are taken and swallowed whole. Angulate
tortoises can drink by sucking water through their
nostrils. They are also known to feed on snails,
insects and animal faeces.

image

SEX and LIFE CYCLES

Males do not defend territories, even though they
live in high densities. Dominant males prevent
other males from mating with females. The
angulate tortoise’s lifespan is more than 30 years
and sexual maturity for both males and females is
reached at 10–12 years. During the mating
season, which lasts from September to April, male
angulate tortoises exhibit intensive male-male
combat. This involves vigorous ramming and use
of the enlarged gular to overturn the opponent.

These battles may be fierce, as breeding males
try to flip one another over until one combatant
runs away or is left on its back. By vigorously
kicking out its legs and shaking its head, an
overturned tortoise can usually right itself. The
kicking and shaking causes the tortoise to rock
from side-to-side until a foot or the head can find
some grip; then it will flip itself over. The
conquered male will wait until the victor has
moved off to right himself. If he is unsuccessful,
he can die from exposure. Larger males usually
win the fights and this gives them access to the
females. For this reason, the males grow larger
than the females (in most other tortoise species
the females are larger). It is not easy for sneaky
male subordinates to mate without being spotted
as tortoise mating is prolonged and noisy.

image

Courtship involves the male in persistent pursuit
of the female with head bobbing, nudging and the
emission of soft grunts. Mounting the female is
facilitated by the male’s concave plastron (the
lower section of the chelonian shell) and in order
to maintain this position, the male will use his
forelimbs to grip the female`s carapace (the upper
section of a chelonian shell). This is then followed
by louder grunts, gasps and wheezes until
copulation eventually happens.
Females can store sperm for extended periods
before using it for fertilisation. The fertilised ovum
is coated by albumen and then a shell layer forms
around the egg. The egg is retained in the tortoise
body for a period that varies from 23 to 212 days,
depending on the ambient temperature and rainfall
(Hofmeyer 2004). Once the egg is fully developed,
rainfall stimulates egg laying and the female will
usually start searching for a suitable nesting site
shortly after the rain has softened the ground. The
hole is about 100 mm wide and within it there is
a smaller chamber about 40 mm wide and deep.
The female uses the claws of her hind feet to
break up the soil, which she then pushes away
with the side of her lower leg. She lays a single,
hard-shelled, round egg, 30–35 × 37–42 mm in
size and weighing 20–25 g. After egg-laying is
completed, the female fills the nest and then
gently tamps down the soil with her shell. The
whole nesting process can take 2 to 3 hours.
Depending on the season, incubation takes 90 to
200 days. Hatchlings weigh 8 to 12 g and emerge
after the first autumn rains. In ideal conditions,
female angulate tortoises can produce six
clutches of eggs per year.

THE BIG PICTURE
Friends and Foes

Chersina angulata has many enemies, the worst of
which are humans. This is because humans are
responsible for habitat destruction through
indiscriminate agricultural and urban development
and illegal collecting of wild tortoises for the pet
trade. The tortoises are also vulnerable to veld
fires; strong, fast wildfires in sandy habitats can
have a negative effect on the population numbers.
Other enemies include small carnivores, baboons,
rock monitors, secretary birds, sea gulls and
crows. Hatchlings have been found skewered on
thorn trees by fiscal shrikes. The domestic dog
can be added to the list and when a tortoise ends
up in the road, some motorists deliberately run
them over.

Smart Strategies

They have a number of tricks allowing them to
withstand dry spells. A tortoise’s skin is dry and
impermeable, so that water loss through the skin
is greatly reduced. During the heat of the day,
tortoises avoid activity, not just to escape
overheating, but also to avoid water loss from dry
wind. They are active in the morning and evening
in late spring and summer, displaying bimodal
activity and sheltering at midday.

They are active
throughout the day at other times. The angulate
tortoise also makes optimal use of scarce water
resources in the dry season, for example it is able
to orientate its body and shell so that the water
droplets that accumulate on its shell during wet
conditions (e.g. dew accumulation in the morning)
flow and accumulate around its head, and the
water is later sucked up through the nose
(Hofmeyer 2009). It is also thought to be able to
survive fire by burrowing into sand or by taking
refuge among rocks (Stuart & Meakin 1983;
Wright 1988).

The angulate tortoise has defence
mechanisms such as the use of its shell as a
refuge and protection when threatened and it will
readily eject the liquid contents of its bowels
when handled, often spraying it some distance.

Poorer world without me
This tortoise eats large quantities of plants, as a
result their scats are full of undamaged seeds.

They are ideal seed dispersers as they defecate
inside bushes giving seeds a better chance of
germination and survival.

People & I
Children are often fascinated when they see
tortoises moving about. They are often kept as
pets, though trade is restricted by regulations.

The angulate tortoise is utilised as a food source
by people living in rural areas of the Karoo.

Conservation status and what the future holds
The angulate tortoise is considered not
threatened, as it is common and abundant in
home ranges. It is, however, listed on the CITES
Appendix II, together with other tortoise species
that are not necessarily now threatened with
extinction but that may become so unless trade
is closely controlled.

In South Africa it is further
classified as a protected species by the Nature
Conservation Ordinance No. 19 of 1974 (as
amended in 2000) and it may not be collected,
transported, or possessed in, or imported into or
exported from, the Western Cape Province without
special permission in the form of a permit from
the relevant conservation authorities. Similarly,
the species is also classified as a protected
species in Namibia. Wild tortoises should be left
in their natural habitat where they belong.

Relatives

The angulate tortoise is the only living species
known from the genus Chersina , but fossil
angulate tortoises dated to approximately 5
million years ago have been found Langebaan
Weg in the southwestern Cape.

Among the extant/
living tortoise species, the angulate tortoise is
closely related to the genus Homopus , which
includes five tiny tortoise species that are also
endemic to southern Africa.

References and further reading

Alexander, G. & Marais, J. 2007. A
guide to the reptiles of southern Africa,
Struik Publishers, Cape Town.

Branch, B. 2008. Tortoises, terrapins &
turtles of Africa. Struik Publishers, Cape
Town.

Boycott, R.C. 1998. The South African
tortoise book: A guide to South African
tortoises, terrapins and turtles .

Southern
Book Publishers (Pty) Ltd,
Johannesburg.

Jacobsen, N. 2005. Remarkable reptiles
of South Africa . Briza Publications,
Pretoria.

Hofmeyer, M. 2009.

Chersina angulata
(Schweigger 1812)—Angulate tortoise,
South Africa Bowsprit tortoise. In:
Rhodin A.G.J, Pritchard P.C.H., Van Dijk
P.P, Saumure R.A., Buhlmann K.A.,
Iverson J.B & Mittermeier R.A (eds).

A compilation project of the IUCN/SSC
tortoise and freshwater turtle specialist
group. Chelonian Research Monographs

No.5.
Hofmeyer, M.D. 2004. Egg production
in Chersina angulata: An unusual
pattern in a Mediterranean climate.

Journal of Herpetology 38: 172–179.

Stuart, C.L. & Meakin, P.R. 1983. A
note on the effect of fire on a population
of angulate tortoises, Chersina angulata

(Cryptodira: Testudinidae) with an
estimate of biomass. Journal of
Herpetological Association of Africa 29:
7, 8.

Wright, M.G. 1988. A note on the
reaction of angulate tortoises on fire in
the fynbos. South African Journal of
Wildlife Research 18, 4: 131–133.

Author
Shireen Harris

Karoo Desert National Botanical Garden

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