The central question
Why did all the handled study packs die whilst an unhandled non-study population persisted and persists to date?
Was this merely coincident with the introduction of invasive handling?
This is the central question concerning the African Wild Dog, one of the most highly endangered, charismatic species of wildlife in Africa, once considered to be a ‘flagship species’ for conservation in the Serengeti. Were the sporadic deaths of study packs in the Serengeti-Mara ecosystem between 1986-89 and the complete demise of all study packs by mid 1991, whilst a non-study population persisted outside protected areas, merely coincident with the introduction of routine invasive research involving anaesthesia, blood sampling and radio-collaring of study packs in 1985 and experimental rabies vaccinations of study packs that began in 1987 in the Mara sector and in 1990 in the Serengeti sector?
“whether handling or vaccinating wild dogs had inadvertently contributed to their demise” David Macdonald (Chairman of IUCN/SSC Canid Specialist Group 1997).
Did the introduction of routine invasive handling, claimed by some researchers to be an ‘essential tool’ for the conservation of the species, lead to the loss of the entire study population of Wild Dog in the Serengeti–Mara ecosystem by mid 1991. Could this also explain the loss of 5 study packs in a three week period in 1996 in Botswana and the dramatic decline between 1989-2005 in the study population of Kruger National Park – the most continuously, intensively and invasively studied population of Wild Dogs in Africa?
- “The feature common to all packs was ‘handling’. Many mammalian species carry latent viruses, including rabies, which can be reactivated by stress in some cases. Handling-induced stress, as measured by highly elevated peripheral serum cortisol concentrations, results from immobilisation of captive wild dogs”. Burrows R. 1992 ‘Nature’. This later became known as the ‘Handling-Stress Hypothesis’
- The publication of a later paper (Burrows , Hofer & East , Proc.R.Soc .Lond. 1994 ‘Demography, extinction and intervention in a small population : the case of the Serengeti wild dogs), prompted the following article in ‘Nature’:
Small populations of endangered species may be driven to extinction by the very researchers whose concern is to keep the animals alive. This dark possibility emerges from further evidence that the packs of wild dogs (Lycaon pictus ) in the Serengeti and Masai Mara that became extinct between 1995 and 1991 were the same ones studied by researchers. R. Burrows et al. (Proc.R. Soc. Lond. B256. 281-292: 1994) re-evaluate their own and others data and alternative hypotheses, and conclude that the most likely explanation for the demise of the study packs is that intervention-induced stress made the animals more vulnerable to rabies. The message is that the effects of field techniques such as trapping, darting, tagging radio-collaring, tissue sampling and vaccination should not be ignored as factors influencing the fate of species under threat. ‘NEWS AND VIEWS, ‘Pack Deaths’ Resume ‘Nature’ Vol. 369. 23 June 1994.
- Is the use of highly invasive research techniques ‘essential’, as is often claimed, for the conservation of endangered species such as the African Wild Dog or are such “tools” used primarily to facilitate the rapid collection of research data for theses and scientific papers, leading to academic advancement of students and their supervisors and funding, often by charities, for their institutions?
Until these central questions and related matters are fully, honestly and openly addressed and, the possibly unique, social structure and behaviour of the African Wild Dog fully recognised and understood, their fate, and possibly that of other endangered species subjected to invasive research, remains uncertain.
INVASIVE RESEARCH also known as ‘HANDLING’ includes anaesthesia, blood sampling and radio-collaring.
Concerns re the use of such techniques have been voiced by some for many years:-
- ‘The majority of workers claim no effect of radio-tracking equipment on their subjects, but this claim is not always justified’ and ‘simple handling and blood sampling have measurable effects on hormonal correlates of stress in captive animals, yet there are few investigations of the effects of analogous treatment of wild animals’. (Colwall et al1998; Gratto-Trevor et al 1991) Cuthill1991.
- ‘Studies of carnivores, in particular, rely heavily on radio telemetry to obtain information from their elusive subjects, but little is known on how handling and tagging affects individuals’ and ‘It is likely, however, that in many studies any adverse effects are either unnoticed, or perhaps because they are rare, or more likely, because they are not reported ‘ Laurenson (1992) thesis.
- ‘Open discussion of past successes and failures [of interventions] is vital to encourage the necessary development of this emerging field’. Woodroffe,R., 1998 IUCN Species Survival Commission Veterinary Specialist Group Newsletter 16.
- ‘A historian has recently written of partisan histories that:- ” loyalty and discretion may result in the suppression of discreditable evidence….” K. Alvarez ( 1993) ‘Twilight of the Panther :- Biology, Bureaucracy and Failure in an Endangered Species Program ‘ , referring to a disastrous attempt to conserve the endangered population of Black-footed ferret in North America.
- ‘If such a mess can be made of efforts to save a creature as attractive as the black-footed ferret in a country as well organized and prosperous as the United States, prospects for conservation in other parts of the world are indeed bleak’. (Robert May ‘Nature’ 1986).
The selective extinction of the Wild Dog Study Packs in the Serengeti-Mara Ecosystem
Prior to 1986 no whole pack extinction in the Serengeti was known other than those shot by rangers/game wardens as vermin, a practice that ceased in 1973. Post 1985 the new phenomenon of disease related study pack extinction in Serengeti paralleled the increasing use of intensive invasive research techniques. Between June 1986-August 1990 (pre Serengeti mass vaccination) 5 widely spaced study packs died (with rabies confirmed in one) all within 4 months of the anaesthetisation and radio-collaring of one or more individuals in the pack; other study and non study packs, some with home ranges overlapping that of the diseased pack, survived each study pack death. There was no evidence of inter-pack transmission of pathogens or of domestic dog vectors.
Between 1986-1991 the entire wild dog study population comprising 14 packs containing approximately 200 individuals died/disappeared from two study areas in the Serengeti-Mara ecosystem of Tanzania and Kenya, East Africa. Of the 13 Serengeti-Mara study packs known to have become extinct 77% survived less than 4 months after the anaesthetisation and radio collaring of one or more individuals in the pack.
A non-study population persisted within and around the ecosystem throughout the period of extinction of the study population and persists to date. The two study populations together with a non-study population formed part of a breeding population with distinctive DNA haplotypes with interchange via long distance dispersal.
The Serengeti and Mara study packs were the subject of research by scientists who routinely used intensive invasive research techniques (known as ‘handling’); including anaesthetization for radio-collaring and blood sampling and, in the Mara study population, sporadic experimental rabies vaccinations (reported as commencing in 1987) were carried out despite the lack of any serological evidence at that stage that packs in the Mara had been exposed to rabies virus. Thus the rationale for the Mara study experiment is unclear. Prior to 1989 rabies had not been confirmed in any free living population of wild dogs. In 1990 a mass rabies vaccination was carried out in the Serengeti study population, by June 1991 all Serengeti study packs were extinct.
After the Serengeti vaccination campaign, blood samples taken up to 2 years before vaccination, were finally screened and 46% were then found to be rabies seropositive. The population had been exposed to rabies in the environment pre vaccination and some survived suggesting that some natural immunity existed pre but not post vaccination.