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Chersina angulataSouth African Bowsprit Tortoise, Angulate Tortoise

By Wynne Waggoner

Geographic Range

Angulate tortoises, Chersina angulata, are native to South Africa along the coastline of Cape Province, and into Namibia (Lever, 2003). The C. angulata range includes East London in the Eastern Cape Province and most of the Western Cape Province. In addition to the western region of Northern Cape Province, the range of C. angulata continues across the Orange river into Namibia (Hofmeyr, 2009). C. angulata are also found on three islands off the southwestern coast of South Africa: Robben, Dassen, and Dryer. They have most likely been introduced to the Dassen and Dryer islands, but are probably native to Robben Island (Harris, 2001). The population of C. angulata is especially dense on Dassen Island. Finally, there is a population of C. angulata recorded in Karoo National Park, in the Great Karoo region (Harris, 2018). (Harris, 2001; Hofmeyr, 2009; Lever, 2003)

Habitat

Angulate tortoises are most often found in and along coastal scrub vegetation, in dry or semi-arid, sandy areas with Mediterranean climates. The angulate tortoise prefers regions with low annual rainfall and temperatures ranging from mild to hot in the summer (23 to 33°C), although inland populations can also be found in moister areas with higher rainfall (Harris, 2001). The Mediterranean habitats where C. angulata are found include Fynbos, Albany Thicket, Succulent Karoo and Nama Karoo (Hofmeyr, 2009). The habitats that C. angulata inhabit mostly consist of dry shrubs and grasses with a sandy substratum that C. angulata likes to bury themselves in. However, they can also occupy more rocky areas (Harris, 2018). (Harris, 2001; Hofmeyr, 2009)

  • Range elevation
    1200 (high) m
    3937.01 (high) ft

Physical Description

The defining trait of Chersina angulata is the long protruding gular portion of the plastron in males, which is where their nickname Bowsprit Tortoise derives (Leone, 2018). The gular is the most anterior part of the plastron, the bottom section of shell. The gular projection is usually only present on the male C. angulata. Shell color can vary based on region, but in general the shell structure and shape are similar across the species.

The top shell, or carapace, is typically composed of (starting from the outer edge going in) eleven paired marginal scutes, four paired costal scutes, and five vertebral scutes in the center. In addition, they have a single supracaudal and a single nuchal scute. The underside of the shell of the tortoise, the plastron, consists of the gular projection and paired humeral, pectoral, abdominal, femoral, and anal scutes. Both sides of the plastron have one or two axillary and one inguinal scute (Hofmeyr, 2009). C. angulata lack buttock tubercles and a terminal spine on the tail. The front limbs have five claws, and the hind limbs have four claws.

Sexual dimorphism in C. angulata is exhibited in size and shell shape. Female C. angulata have a rounder body shape, a smaller tail, a thicker midsection, and a flat plastron. Male C. angulata tend to be flatter, longer, wider, and have a concave plastron. Female angulate tortoises range from 168 to 200 mm in length, and males from 180 to 254 mm in length. The mean lengths are 168 mm and 187 mm for females and males, respectively. The mean weight for females is 813 g, and 916 g for males (Hofmeyr, 2009). The angulate tortoise populations on Dassen island have been known to be significantly larger than average sizes, with one being recorded at 351 mm in length and a mass of 3939 g.

Hatchlings typically weigh between 10 to 12 g, and are 30 to 39 mm long (Hofmeyr, 2009). It is not known when sexual dimorphism develops in the angulate tortoise, but it must happen before both males and females reach sexual maturity at 10 to 12 years, due to mating systems and behavior.

Shell color can vary based on region, but in general the vertebral and costal scutes have dark centers surrounded by light colored (often yellow) areolae, which have dark brown or black growth rings. The marginal scutes tend to be light-yellow with a dark triangle in the center (Harris, 2018). The amount of yellow and black as well as the color of the plastron varies across regions. The tortoises in the western regions have a redder plastron, and the tortoises in the eastern regions are smaller and have more yellow plastrons (Leone, 2018). (Harris, 2001; Hofmeyr, 2009; Leone, 2001)

  • Sexual Dimorphism
  • male larger
  • sexes shaped differently
  • ornamentation
  • Range mass
    813 to 916 g
    28.65 to 32.28 oz
  • Range length
    168 to 304.8 mm
    6.61 to 12.00 in

Development

After mating, female Chersina angulata are able to store sperm for an extended period of time before using it to fertilize their egg. The fertilized ovum, coated by albumen and a shell layer, can be retained in the female tortoise anywhere from 23 to 212 days. The timing of C. angulata egg release depends on several environmental factors including ambient temperature and rainfall. Rainfall stimulates the process of egg laying and softens the ground, and the female C. angulata will begin searching for a nesting site. Females dig small holes and lay a single, round, hard-shelled egg with dimensions around 30 to 35 mm by 37 to 42 mm, and a mass of approximately 20 to 25 g (Harris,2018). The females will usually lay between two to six eggs per year. After egg laying, females will fill the hole with dirt and pat it down. The egg can incubate for 90 to 200 days and hatch in early autumn, after the first rainfall. The hatchling success rate is pretty high at 80%, and hatchlings can weigh from 8 to 12 g. Angulate tortoises can live for upwards of 30 years (Hofmeyr, 2009). (Harris, 2001; Hofmeyr, 2009)

Reproduction

Angulate tortoises typically mate between September and April (Harris, 2018). Mating systems revolve around the males combat and territory. Dominant males fight each other for females, and sometimes just to prevent other males from mating. Male Chersina angulata violently ram each other and use their gular projections to try and flip each other over. They continue to battle until one is flipped over or runs away. If a male angulate tortoise gets flipped onto its back and is unable to flip back over, he will likely die of exposure. Usually, larger males win fights and mate with the female. Males attract mates by bobbing heads, nudging females, and grunting softly. The concave plastron of the males allows them to mount females from behind, grasp her shell with his forelimbs, and copulation occurs. (Harris, 2001; Hofmeyr, 2009; "Chersina angulata, 030", 2007)

Both females and males reach sexual maturity between 10 to 12 years, and breeding season is from September to April (Harris, 2018). Females can lay between two and six clutches per year, depending on environmental conditions, and each clutch contains a single egg (Joshua, Hofmeyr, Henen, 2010). The female retains the egg for a period of 23 to 212 days and lays the egg in a hole in the ground. The egg incubates for 90 to 200 days. While tortoises can be protective over their nests, once the eggs hatch, the hatchlings are pretty much on their own (Harris, 2018). (Harris, 2001; Hofmeyr, 2009; Joshua, et al., 2010; Lever, 2003)

  • Breeding interval
    Females can lay between two to six clutches per year, with each clutch containing a single egg.
  • Breeding season
    Breeding season is between September and April.
  • Range number of offspring
    1 to 1
  • Range gestation period
    90 to 200 days
  • Range age at sexual or reproductive maturity (female)
    10 to 12 years
  • Range age at sexual or reproductive maturity (male)
    10 to 12 years

Female Chersina angulata can be protective of their nests, but otherwise exhibit no parental investment. Once the eggs hatch, the hatchlings are not cared for. (Lever, 2003)

  • Parental Investment
  • no parental involvement
  • pre-hatching/birth
    • protecting
      • female

Lifespan/Longevity

Angulate tortoises can live for more than 30 years, but little is known beyond that. Due to a lack of knowledge on husbandry and incubation, it is very rare to have angulate tortoises in captivity or breed them, and therefore little is known about the lifespan in captivity (Leone, 2018). (Leone, 2001)

  • Average lifespan
    Status: wild
    30+ years

Behavior

Chersina angulata are active throughout the year, and activity levels depend on temperature and rainfall. Sun and rain tend to increase activity levels of feeding. Active behaviors such as feeding and fighting occur during high temperatures. In the spring, both males and female angulate tortoises spend long hours basking under the cover of sparse vegetation (Lever, 2003). In general, tortoises are loners, and only come together during mating season. (Hofmeyr, 2009; "Chersina angulata, 030", 2007; Lever, 2003)

  • Range territory size
    2200 to 16000 m^2
  • Average territory size
    2800 m^2

Home Range

In the Eastern Cape Province of South Africa, both male and female angulate tortoises have similar small home ranges around 0.28 ha (Hofmeyr, 2009). However, in Western Cape Province, female C. angulata tend to have larger home ranges (approximately 1.6 ha) than male C. angulata (approximately 0.25 ha). (Harris, 2001; Hofmeyr, 2009; Joshua, et al., 2010)

Communication and Perception

Angulate tortoises are solitary animals and do not communicate with one another outside of mating season. (Harris, 2001)

Food Habits

The diet of Chersina angulata is not very well known, but in general angulate tortoises are herbivorous and feed on annuals, grasses, flowers, and other plants including succulents (Joshua et al., 2010). C. angulata have also been known to eat snails, insects, moss, mushrooms and the occasional animal feces (Harris, 2018). C. angulata have no teeth, so all their food is eaten in small bites using their beak. (Harris, 2001; Hofmeyr, 2009; Joshua, et al., 2010)

  • Animal Foods
  • insects
  • mollusks
  • Plant Foods
  • leaves
  • seeds, grains, and nuts
  • flowers
  • bryophytes
  • Other Foods
  • fungus
  • dung

Predation

Angulate tortoises have many natural small animal predators, including small carnivores (such as jackals, mongoose, badgers) predatory birds, baboons and more. Fiscal shrikes (Lanius collaris) impale hatchlings on thorns, and the hatchlings are also targeted by Pied Crows (Corvus albus) (Hofmeyr, 2009). There is currently no information on anti-predator adaptations or behaviors. (Harris, 2001; Hofmeyr, 2009)

Ecosystem Roles

Angulate tortoises are ideal seed dispersers because they eat large quantities of plants and then defecate the undamaged seeds. The dispersal of seeds by C. angulata helps the survival of many different plant species (Harris, 2018). There is very little information on the role of C. angulata in the ecosystem. (Harris, 2001)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

Angulate tortoises are not of great economic importance to humans. Some children and families capture them from the wild and keep them as pets, so there is possibly a small pet trade. Also, Chersina angulata are occasionally used for food by local people. Sometimes people use their shells for a variety of objects such as jewelry, tourist trinkets and wall ornaments. (Joshua, et al., 2010)

  • Positive Impacts
  • pet trade
  • food
  • body parts are source of valuable material
  • research and education

Economic Importance for Humans: Negative

Angulate tortoises are not known to have any negative economic effects on humans. (Hofmeyr, 2009; Lever, 2003)

Conservation Status

Chersina angulata is listed as least concern on the IUCN Red list. This species is not listed with the US Federal List because it is only found in South Africa. This species is listed in Appendix I and II in CITES.

Other Comments

Chersina angulata is called Bowsprit Tortoise due to the presence of a gular projection on the males. The gular projection is a long extension of the plastron that protrudes under the neck and is said to resemble a bowsprit (Leone, 2018). A bowsprit is a spar that extends from the bow of a sailing ship, which is to say a wooden projection on the front of the hull of a ship. (Leone, 2001)

Contributors

Wynne Waggoner (author), Colorado State University, Nathan Dorff (editor), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

coprophage

an animal that mainly eats the dung of other animals

delayed fertilization

a substantial delay (longer than the minimum time required for sperm to travel to the egg) takes place between copulation and fertilization, used to describe female sperm storage.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

detritivore

an animal that mainly eats decomposed plants and/or animals

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

insectivore

An animal that eats mainly insects or spiders.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

solitary

lives alone

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

"Angulate Tortoise" (On-line). iNaturalist. Accessed March 21, 2021 at https://www.inaturalist.org/guide_taxa/705841.

"Angulate tortoise" (On-line). SCARCE. Accessed March 21, 2021 at https://web.archive.org/web/20180502085103/http://academic.sun.ac.za/capeherp/cederberg/chelonianangulate.htm.

"Bowsprit Tortoise" (On-line). Honolulu Zoo. Accessed March 21, 2021 at https://web.archive.org/web/20081004193621/http://www.honoluluzoo.org/bowsprit_tortoise.htm.

IUCN Tortoise and Freshwater Turtle Specialist Group. 2007. "Chersina angulata, 030" (On-line). IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Accessed March 21, 2021 at https://iucn-tftsg.org/chersina-angulata-030/.

"Chersina angulata" (On-line). Reptile Database. Accessed March 21, 2021 at https://reptile-database.reptarium.cz/species?genus=Chersina&species=angulata.

Harris, S. 2001. "Angulate Tortoise" (On-line). SANBI. Accessed March 21, 2021 at https://www.sanbi.org/animal-of-the-week/angulate-tortoise/.

Hofmeyr, M. 2009. Chersina angulata (Schweigger 1812) – Angulate Tortoise, South African Bowsprit Tortoise. Conservation Biology of Freshwater Turtles and Tortoises: 030.1-030.6. Accessed March 21, 2021 at https://iucn-tftsg.org/wp-content/uploads/file/Accounts/crm_5_030_angulata_v1_2009.pdf.

Joshua, Q., M. Hofmeyr, B. Henen. 2010. Seasonal and Site Variation in Angulate Tortoise Diet and Activity. Journal of Herpetology, Volume 44 No.1: 124-134. Accessed March 21, 2021 at https://www.jstor.org/stable/40665013?seq=1.

Leone, C. 2001. "The Angulate Tortoise Of South Africa" (On-line). Reptiles Magazine. Accessed March 21, 2021 at https://www.reptilesmagazine.com/the-angulate-tortoise-of-south-africa/.

Lever, C. 2003. Naturalized Reptiles and Amphibians of the World. Oxford New York: Oxford University Press.

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