There are 11 species of gazelles in the genus Gaze/la. Currently, the In- ternational Union for the Conserva- tion of Nature (IUCN) estimates nine gazelle taxa to be threatened or endangered’. Recent information compiled by the IUCN Antelope Specialist Group and distributed in Gnuslettersuggests that the plight of most gazelle taxa is grim indeed*.

This dire forecast is reinforced by a recent article by Mostafa A. Saleh in Biological Conservation, on the sta- tus of gazelles in Egypt3. Although hunting pressure, agricultural and urban expansion and industrial activ- ities have been considered to have adverse effects on gazelle popula- tions and habitats, the extent of the impact of destructive human activ- ities on populations of gazelles and their status has not been recently documented. Between 1980 and 1985 Saleh surveyed localities in Egypt where G. dorcas or G. lepto- ceros leptoceros had previously been sighted or museum specimens collected. His survey area included large portions of the eastern and western desert, the coastal desert belt and the Sinai Peninsula. For both species, the number of locali- ties where gazelle populations could still be found had decreased. The northern portion of the western desert was most severely affected; here, populations of both G. dorcas and G. I. leptoceros have been extir- pated.

Conservation biology of captive populations Gazelles are elegant, diminutive

antelopes whose systematics and taxonomy have presented formid- able challenges. Specific and sub- specific differences in gazelles have been based on relatively subtle char- acters such as size and curvature of horns as well as pelage coloration. Recent taxonomic revisions have questioned the validity of some pre- viously named taxa4s5. In the context of conservation, the significance of the perceived minor characteristics that were used to differentiate sub- species has been called into ques- tion.

Genetic studies, especially recent chromosomal studies of gazelles in captivity, have provided evidence for unanticipated genetic subdivision in some species of gazelles6G7 achieved mainly through centromere fusion (robertsonian) rearrangements. Most gazelle species share a particular translocation between the X- chromosome and an autosomes. A significant exception is G. thomsoni,

Oliver Ryder is at the Center for Reproduction of Endangered Species, Zoological Society of San Diego, PO Box 551, San Diego, CA 92112, USA.

TREE voi. 2, no. 6, June 1987

Conservation Action for Gazelles: An Urgent Need

Oliver A. Ryder

possessing a karyotype of mainly acrocentric elements and lacking the X-autosome translocatior+.

A dramatic example of chromosomally-based outbreeding depression has been documented for zoological park specimens clas- sified as G. soemmerringi. In a study of 28 individual specimensg, three independent robertsonian transloca- tion events were documented, pro- ducing karyotypes varying in diploid number from 34 to 39. The reduction in numbers of captive G. soemmer- ringi is currently attributed to the decrease in fitness that is assumed to accompany the production of sig- nificant numbers of duplication/ deficiency gametes and resultant zygotes, although this has yet to be tested directly. The possibility exists that, in constituting a captive found- er population for this species, in- advertant sampling of cryptic spe- cies, differing in chromosomal con- stitution, occurred. Alternatively, in the process of capture, transport and quarantine of founder stock for North American zoos, hybridization with another gazelle species (such as G. granti) may have occurred with subsequent hybrid breakdowns.

Thirteen taxa of gazelles are held in captivity in zoological parks that participate in the International Spe- cies Inventory System (ISIS)lo. Cap- tive gazelle populations are com- monly derived from very small num- bers of wild-caught individuals, For example, the captive population of Speke’s gazelle (G. spekei) consists of seven males and fifteen females derived from one male and three female founders”. Inbreeding de- pression was manifested as a reduc- tion in birthweight and an increased probability of neonatal demise associated with the degree of con- sanguinity of the parents. Extinction of the zoo population was possible. So far, a reprieve has been managed by selecting as parents of the next generation individuals that are them- selves inbred and, by definition, have reduced genetic load. Of course, the cost of invoking this ex- treme breeding strategy is the deple- tion of neutral allelic variation12.

ISIS reports that, as of June 1986, 877 individuals of the genus Gazella were held in reporting institutionslO. All gazelle taxa held in captivity rep- resent very small populations from the population geneticist’s stand-

Slender-horned gazelle (Gaze//a leptoceros leptoceros). Photograph reproduced by permission of the Zoological Sociery of San Diego.

TREE vol. 2, no. 6, June 1987

point. Furthermore, the ISIS census population sizes for some taxa, e.g. G. dorcas, G. rhomsoniand G. soem- merringi, are declininglo. Thus, the prospect for conservation of gazelle gene pools in captivity is not en- couraging. Unfortunately, the ac- quisition of new founder individuals is problematical, and is complicated by the declining status of wild populations, lack of information about the capture location of the ancestors of existing zoo stocks, impor+export regulations, and cost- ly intermediate-site quarantine re- quirements.

The status of wild populations Development of hydroelectric

power facilities is placing important gazelle habitats under threat in Egypt and, in general, destruction of habi- tat is a major threat to survival of gazelle speciess. However, human predation may, at the moment, play an even larger role in the disappear- ance of gazelles. Where hunting occurs, gazelle populations have been severely reduced or extirpated, as in the western desert of Egypt where overhunting is clearly indi- cated as a major cause of decline in G. dorcas and G. 1. leprocero3.

On the other hand, gazelle popula- tions may proliferate even in the vicinity of human settlements, pro- vided hunting is limited. In Israel, the increase of G. dorcas populations documented in another article in Biological Conservation, by Yom- Tov and Ilani13, provides some optimism that human activities and gazelle populations can coexist. Over a 20-year period, G. dorcas popula-

tions have increased at an average dorcas populations elsewhere in the annual rate of 9.1% near agricultural species’ range is largely unknown’. settlements and 3.8% in other areas. However, in the same period, Conclusion populations of a previously unde- A limited time is available for con- scribed subspecies of G. gaze/la in servation intervention to save the Negev desert study area de- locally-adapted gene pools, and to creased at an average annual rate of prevent the impending extinction of 0.6% to an estimated population in local populations, subspecies and 1985 of 27 animalsl3. species of gazelles. Ex situ conserva-

Further caution may be warranted: tion prospects for gazelles may im- in proximity to human agricultural prove as zoos develop further exper- activities, concentrations of gazelles tise in husbandry and management. may be at risk of exposure to infec- However, current efforts in zoos suf- tious agents that have devastating fer from insufficient founder stock, effects. For instance, foot-and-mouth inbreeding, and presumed introgres- disease recently had a catastrophic effect on the Ramat Yissichar popu-

sions. Captive breeding efforts in zoological parks, especially involving

lation of G. g. gaze//a14. any newly-imported stock, should The range of the Egyptian slender- be preceded by complete chromo-

horned gazelle (G. 1. leptoceros) has somal studies and should include been extensively diminished3. It sur- detailed information about the sites vives in areas that are remote and of capture of all specimens. inaccessible to motorized vehicles. In the Wadi el Raiyan area, for example,

There is an urgent need for the

the only documented extant popula- protection of existing populations of

tion of wild G. 1. leproceros survives gazelles, the establishment of cap- tive breeding programs for the ex-

as a population of 8-15 animals. Saleh reports that most of the sand

pressed purpose of reinforcing wild populations and, in conjunction with

dune habitat of Wadi el Raiyan will these activities, an increased effort to be destroyed in the next few years by the man-made Lake El Raiyan that

understand the natural history and systematics of these remarkable and

already covers a previous site where fragile creatures. G. 1. leptoceros was collected in 1966. It is possible that remnant populations of G. 1. leptoceros may only survive in Egypt in those rarely References visited areas, south and west of 1 IUCN (1986) 7986lUCNRedListof

Saleh’s survey area, that are relative- ~~hrea~e”edAn’~ma’s,‘UCN 2 Gnusletter (Estes, RD., ed.), IUCN/SSC

ly protected from hunters by their Antelope Specialist Group remoteness and relative inaccessibil- ity.

3 Saleh, M.A. (1987) B/o/. Conserv. 39, 83-95

In captivity the slander-horned 4 Groves, C.P. (1964) z. Sdugetier/c 34, gazelle is increasing in numbers: 38-60 approximately 100 living animals 5 Gentry, A.W. (1971) in The Mammals of are listed in the International Stud- Africa: An Identification Manual (Pt 15.1)

book’“. However, in this taxon and in (Meester, J. and Setzer, H.W., eds),

G. spekei, small population effects, pp.86-93 Smithsonian Institution Press 6 Benirschke, K. (1985) Symp. Zoo/. Sot.

such as high neonatal mortalities Land, 54 7,_87 associated with inbreeding and los- 7 Benirsihke, K. and Kumamoto, A.T. La ses of genetic variability through Kromosomo, 11-45 (in press) drift, are depleting genetic variability in the captive populations.

8 Effron, M., Bogart, M.H., Kumamoto, A.T. and Benirschke, K. (1976) Genetica

Gaze//a dorcas is a widely distribu- 46,419-444 ted species that occupies a variety of 9 Benirschke, K., Kumamoto, A.T., Olsen, desert habitats throughout North J.H., Williams, M.M. and Oosterhuis, J.

Africa. The variability in a species (1984) Z. SBugetierk. 49,368-373

with so large a distribution has led to 10 ISIS (1986) Species Distribution

as many as ten trinomial names. Reports, International Species Inventory

However, it is not clear whether a System

single large contiguous population ii Read, 6. (1987) International Studbook for Gazella spekei, St. Louis Zoological

existed, providing opportunity for Park (USA) gene flow, or whether isolated, allo- 12 Templeton, AR and Read, B. (1984) patric populations were established &JOB~O/. 3,177-199 long ago around the sandy centers of 13 Yom-Tov, Y. and Ilani, G. B;o/.

the Sahara5. Nonetheless, the range co”serv. 40(in press’ of G. dorcas has diminished in recent 14 Schuster, R. (1986) GnusletterJanuary

years in Egypt3. It survives in several 1986,6

sites, for example in the mine field 15 Penny, C. (1987) International

areas close to the Gulf of Suez and StudbookforGazella leptoceros

around major roads. The status of G. Ieptoceros, Zoological Society of San Diego (USA)