Study

Hatching success and juvenile growth of Nile crocodile Crocodylus niloticus at Kariba, Binga and Victoria Falls crocodile farms, and survival in the wild of captive-reared releases, Zimbabwe

  • Published source details Blake D.K. & Loveridge J.P. (1975) The role of commercial crocodile farming in crocodile conservation. Biological Conservation, 8, 261-272

Summary

Commercial crocodile farms in Rhodesia (now Zimbabwe) may have a role in the conservation of Nile crocodile Crocodylus niloticus, a declining species over much of Africa. Legislation stipulated that when crocodile eggs are collected from the wild, a quota of juveniles equivalent to 5% of the number collected must be released at 3 years of age into suitable habitat. Hatching success and juvenile growth was compared with wild populations, and subsequent survival of captive-reared releases assessed.

At the time of study three crocodile rearing stations were present in Rhodesia, Kariba, Binga and Victoria Falls (located in the northwest of the country) operating under permits issued by the Department of National Parks and Wildlife Management.
 
Data of eggs collected and hatched from 1967 to 1973 by these rearing stations were collated; hatching success and juvenile growth was compared with wild populations. Survival and growth of captive-reared releases was assessed by mark and recapture surveys of individuals releasedinto the wild at Lake Kariba.

Hatching success: Hatching success on rearing stations was better than for wild populations.Over the study period 22,679 wild eggs were collected, of these 16,697 (73.6%) hatched. Data available on hatching success in the wild varies greatly, for example: nest predation recorded at 49.4% three weeks after laying (Rhodesia); in a Kenyan study, six clutches had a hatching success of 68.6-96.4%, but another five failed; in a Ugandan study, 55.1 % of clutches were predated and some lost to flooding and damp, thus eggs in only 30% of nests hatched.
 
Growth: Juvenile growth rate on rearing stations was variable but around twice that of wild individuals.
 
Survival: Juvenile mortality on the rearing stations averaged around 50% to 3-years of age; there was a clear trend indicating that as operators became more experienced this high loss was reduced. No comparative information is available for wild populations but mortality rates are thought to be very high.
 
Of 355 juvenile crocodiles returned for release, 53 were marked and liberated at Lake Kariba. Twenty (37.7%) were caught at least once in twice-yearly recapture exercises undertaken since 1970. This survival rate was considered good; growth slowed substantially.
 
Juveniles for release have proved valuable for restocking suitable areas and supplementing natural recruitment.
 
 
Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://www.science-direct.com

Output references

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, terrestrial mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 17

Go to the CE Journal

Subscribe to our newsletter

Please add your details if you are interested in receiving updates from the Conservation Evidence team about new papers, synopses and opportunities.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape Programme Red List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Bern wood Supporting Conservation Leaders National Biodiversity Network Sustainability Dashboard Frog Life The international journey of Conservation - Oryx British trust for ornithology Cool Farm Alliance UNEP AWFA Butterfly Conservation People trust for endangered species Vincet Wildlife Trust