A4.24S Student

Activity 4.24 Putting them back

Purpose • To highlight some of the complications of releasing captive-bred animals back into the wild using the example of the release of captive-bred black-and-white ruffed (Varecia variegata variegata) back into their native forests of Eastern Madagascar. • To examine some data on the captive breeding of the Mauritius kestrel which provides an example of how captive breeding can be highly effective. Ruffed reintroduction

Figure 1 Varecia variegata variegata ready for release. In order to ensure that a reintroduction programme is going to work it is vital that research is conducted to find out exactly how well captive-bred individuals can survive in the wild. Back in 1997 a plan was put into action to release some captive-bred black-and-white ruffed lemurs (Varecia variegata variegata) back into their native forest in the northwest of Madagascar. The plan was drawn up by the Madagascar Fauna Group, a collection of conservation organisations concerned with biodiversity conservation on the island. The group includes the Durrell Wildlife Conservation Trust based at . The Betampona forest reserve was chosen as the release site as it was a protected site and research had shown that the area could benefit from an increase in the wild Varecia population. The following is an extract from Lemur News, a web-based journal produced by the Madagascar Fauna Group. Study this report on the release of captive-bred black-and-white ruffed lemurs before completing the questions that follow.

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Extract As previously reported the Madagascar Fauna Group have been attempting an experimental reinforcement of captive-bred black-and-white ruffed lemurs (Varecia v. variegata) in the Betampona Reserve since 1997 (Britt et al. 1998, 2000). Whilst some individuals have shown encouraging signs of adaptation to a wild existence, others have adapted poorly. However, regardless of the degree of adaptation it is clear that captive-bred individuals of this species are extremely vulnerable to predation by a cat-like carnivore [actually a civet, family: Viverridae] called the fossa (Cryptoprocta ferox). This paper will discuss the impact of this predator on the success of the project and its implications for future reinforcement or reintroduction efforts. The release programme Of the 13 captive-bred V. v. variegata released to date, five (two males, three females) have been killed by C. ferox. Of these five, one pair produced triplets in October 1999, and at least one of these offspring is also presumed to have fallen victim to C. ferox predation. It is particularly disappointing that this pair who had been able to reproduce and raise triplets were killed. Of the remaining animals one male died as a result of injuries sustained during a fall or possibly malnutrition and another female simply disappeared. One male from the November 1997 release is integrated into a wild group and thriving. A female released in November 1998 has been withdrawn from the programme following the killing of her two fellow releasees by C. ferox, but also due to her poor adaptation over a period of 2 years in the forest. Three males and one female released in January 2001 are still surviving and showing good signs of adaptation in terms of food location, travel and navigation within the forest. Preliminary analyses of behavioural data indicate that individuals with early or long-term experience in enclosures that simulate the natural forest environment of this species adapt better to life in the wild. This has been the case for both the first and third release groups. For both groups it has been possible to stop supplemental feeding within a few months of release. Also both groups have shown similar ranging patterns to wild V. v. variegata and have established territories of comparable size. However, the second release group had very limited experience (a few months) in ‘natural habitat enclosures’ and remained reliant on provisioning throughout their 2 years in the forest. This group showed no inclination to range far from their release site in search of food. Extract from Britt, A., Welch, C. and Katz, A. (2001), The impact of Cryptoprocta ferox on the Varecia v. variegata Reinforcement Project at Betampona, Lemur News 6, 35–37. Lemur News provides reports on other lemur species and conservation work being conducted in Madagascar on this unique group of mammals. The website for Lemur News can be found in the weblinks that accompany this activity.

Q1 What was the fate of the released captive-bred lemurs? Q2 What percentage of the released lemurs survived? Q3 Why was ‘supplemental feeding’ carried out on the release group? Q4 Do the results give any indication that captive-bred lemurs can be successfully released into the wild? Q5 Suggest what modifications a zoo could make to their reintroduction programme to increase the chances of successful release into the wild. Q6 Give reasons for the inclusion (or non-inclusion) of juvenile or adult lemurs in the release programme.

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Saving the Mauritius kestrel Table 1 shows the changes in population size for the Mauritius kestrel (Falco punctatus) from its low point in 1973, with only two known pairs surviving in the wild, up to 1990. Direct management of the wild population began in 1983. This involved a combination of fostering captive-bred kestrels by wild pairs and release of captive-bred fledglings. By 2002 the wild population was over 350 pairs and the population had stabilised. The species was reclassified, from endangered to vulnerable.

Using a spreadsheet (or graph paper) draw a graph of the data to illustrate the changes that took place between 1973 and 1990. Use this to answer the questions that follow. Table 1 Changes in population size of the Mauritius kestrel. Season Total population Natural Number of captive Number production fledglings released fostered 1973 4 0 1974 6 2 1975 6 0 1976 12 6 1977 15 6 1978 16 5 1979 18 4 1980 20 4 1981 17 3 1982 20 8 1983 20 5 5 1984 34 12 12 12 1985 35 8 13 8 1986 34 8 12 8 1987 48 8 24 10 1988 62 8 26 12 1989 110 10 55 28 1990 135 12 53 24 Source: The data are from a paper by Carl Jones, Mauritius Wildlife Fund (Dodo Journal, published by DWCT).

Q7 Explain the impact of releasing captive-bred kestrels on the total wild population. Q8 Based on the shape of the graph for natural production do you think that the species would have gone extinct over time without the release of captive-bred stock? Q9 What natural events could have caused the natural population to go extinct if numbers had remained low over a long period? Q10 One argument for increasing population size rapidly when the original population of a species is low is that it generates more individuals, some of which should be able to survive the impact of inbreeding. What could have happened to the wild kestrel population as a result of inbreeding? The Mauritius Wildlife Foundation website provides additional information on the kestrel and other species currently being brought back from the brink of extinction on the island of the dodo. The website is in the weblinks that accompany this activity.

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