Contraception, reproduction and demography of free-ranging Etosha lions (Panthera leo)

The use of long-acting contraceptives as an effective population control mechanism for free-ranging lions was investigated during a three-year study in the Etosha National Park on five lion prides. Lions were immobilized with ketamine hydrochloride and xylazine hydrochloride. Following immobilization, lionesses were weighed, measured and aged, while serum steroid hormone levels were analysed and vaginal smears were obtained. Physical condition and sexual state were assessed. Individuals were used as control animals or given melengestrol acetate (contraceptive) implants, branded and released; the animals were observed for possible changes in behaviour, birth rate and mortality. Ten treated lionesses were recaptured at irregular intervals to reassess weight and steroid hormone levels, while three lionesses had their implants removed to determine if their fertility would return. The contraceptives prevented pregnancy, were reversible when removed and did not alter lion behaviour significantly, except that sexual behaviour was not recorded in treated lionesses.     

Twenty polymorphic microsatellite markers in the Asiatic lion (Panthera leo persica)

The Asiatic lion (Panthera leo persica) is driven to a single habitat in Gir forests in India for its survival. In order to devise adequate conservation and management strategies for this critically endangered species, it is important to characterize its genetic diversity and understand its population structure. Here we report twenty microsatellite loci, in addition to seven reported earlier, from the genome of a pure Asiatic lion. The microsatellite loci described here will provide potentially useful markers for the assessment of genetic variability in the only existing wild population of the Asiatic lions and other big cat species.     

Developmental changes in pituitary-gonadal function in free-ranging lions (Panthera leo leo) of the Serengeti Plains and Ngorongoro Crater

Pituitary-gonadal function was examined in male lions free-ranging in the Serengeti Plains or geographically isolated in the Ngorongoro Crater of Tanzania. Lions were classified by age as adult (6.1-9.8 years), young adult (3.3-4.5 years) or prepubertal (1.4-1.6 years, Serengeti Plains only). Each animal was anaesthetized and then bled at 5-min intervals for 100 min before and 140 min after i.v. administration of saline or GnRH (1 micrograms/kg body weight). Basal serum LH and FSH concentrations were similar (P greater than 0.05) among age classes and between locations. In Serengeti Plains lions, net LH peak concentrations after GnRH were approximately 35% greater (P less than 0.05) in prepubertal than in either adult or young adult animals. GnRH-stimulated LH release was similar (P greater than 0.05) between adult and young adult lions, and these responses were similar (P greater than 0.05) to those measured in Ngorongoro Crater lions. Basal and GnRH-stimulated testosterone secretion was higher (P less than 0.05) in adult than in young adult lions and lowest (P less than 0.05) in prepubertal lions. Age-class differences in testosterone production were related directly to the concentrations of LH receptors in the testis (P less than 0.05). Basal and GnRH-stimulated testosterone secretion and gonadotrophin receptor concentrations within age classes were similar (P greater than 0.05) between lions of the Serengeti Plains and Ngorongoro Crater. Lower motility and higher percentages of structurally abnormal spermatozoa were observed in electroejaculates of young adult compared to adult Serengeti Plains males (P less than 0.05) and were associated with decreased steroidogenic activity. In contrast, there were no age-related differences in ejaculate characteristics of Ngorongoro Crater lions. Seminal quality in the Crater population was poor in adult and young adult animals and was unrelated to alterations in pituitary or testicular function. In summary, only seminal quality in adult male lions was affected by location, whereas age significantly affected both basal and GnRH-stimulated testosterone secretion and seminal quality (Serengeti Plains only) in sexually mature males. The striking seminal/endocrine differences among pride (breeding) males of different ages raises questions about the impact of age on individual reproductive performance in this species.     

Reversible immobilization of free-ranging African lions (Panthera leo) with medetomidine-tiletamine-zolazepam and atipamezole

A combination of medetomidine-tiletamine-zolazepam was used to conduct six immobilizations of free-ranging lions (Panthera leo) in Waza National Park, Cameroon, during 1999 and 2000. Drugs were administered by dart injection at 0.07+/-0.01 (mean+/-SD) mg/kg of medetomidine and 1.8+/-0.5 mg/kg of tiletamine-zolazepam. Chemical immobilization was characterized by smooth inductions (14.1+/-6 min), satisfactory analgesia, and muscle relaxation. One animal was treated for bradypnea. No major alterations of physiologic parameters (heart and respiratory rates, rectal temperature) were seen during immobilization in the other lions. Relative arterial oxygen saturation was measured in two animals and revealed mild hypoxemia. The animals received atipamezole at 0.3+/-0.1 mg/kg intramuscularly for reversal of anesthesia. Recoveries were uneventful. All animals were radiocollared, and no mortalities occurred during an 18-mo follow-up period. Use of medetomidine-tiletamine-zolazepam for anesthesia and reversal of anesthesia with atipamezole appear to be useful for reversible immobilization of free-ranging lions.     

Comparative growth of wild male and female lions (Panthera led)

Lion growth was studied by fitting sex specific Von Bertalanffy curves and linear regressions to data on body mass, heart girth, shoulder height and vertebral column length. Measurements were recorded for 344 lions ( Panthera leo ) (158 ♂♂ and 186 ♀♀), from Kruger National Park, South Africa. Growth in mass for males and females was linear up to about 36 months of age 0 = 0–98 and 0–99 respectively). The other age-specific measurements were clearly curvilinear. Mean weights for adult lions (excluding stomach contents) were 187–5 kg (♂♂) and 124–2 kg (♀♀) respectively. Lions tended to continue growing up to about seven years in males and nine to 10 years in females after which they usually started to lose condition. Body mass and heart girth measurements of Kruger Park lions were compared with samples from three other populations. These showed that lions from East Africa were smaller than those from more southern populations in Rhodesia, Kalahari and Kruger Park.     

Prevalence of hematozoans in lions (Panthera leo) and cheetah (Acinonyx jubatus) in Serengeti National Park and Ngorongoro Crater, Tanzania

Lions (Panthera leo) and cheetah (Acinonyx jubatus) from the Serengeti National Park and Ngorongoro Crater Conservation Area, Tanzania were examined for the presence of blood protozoans. Twenty-eight percent of the lions were infected with Trypanosoma sp. and the prevalence of trypanosome infection varied significantly between adjacent habitats. All of the animals were infected with Hepatozoon sp. and a Theileria sp.-like piroplasm that was morphologically indistinguishable from Theileria felis.     

The risk of inbreeding due to habitat loss in the lion (Panthera leo)

A major concern in conservation biology is toavoid inbreeding depression in smallpopulations. Inbreeding has been shown to causeloss of fecundity and reduced survival innatural populations. To predict futureinbreeding levels, given changes in ecologicalconditions, data from large outbred populationsare needed. I use recent population geneticmodels to show how genetic data from such apopulation, combined with ecological data canbe used to predict future changes in levels ofinbreeding. In particular, data from the lion(Panthera leo) is used to simulate theeffect of habitat loss on the future levels ofinbreeding. To do this I used a deterministicpopulation genetics models and anindividual-based stochastic model. Two factorsstand out as particularly important: totalnumber of prides and male dispersal rates. Ifprides are very few (= 10) inbreeding (F)will increase from 0.0 in the initial state to0.26–0.45 after 30 generations, while if thenumber of prides is 100 this level is onlyaround 0.05 assuming no migration into thepopulation. Habitat heterogeneity had onlyminor effects. A reduction in male dispersalfrom their natal territory from 100% to 95%increased the level of inbreedingsubstantially, and never reached below F 0.25 regardless of the number ofprides. Therefore, to sustain a large outbredpopulation of lions, a continuous population ofat least 50 prides, but preferably 100 prides,with no limits to dispersal is required.     

Immobilization of free-ranging African lions (Panthera leo) with a combination of xylazine hydrochloride and ketamine hydrochloride

The combination of 55 mg/ml xylazine hydrochloride and 200 mg/ml ketamine hydrochloride was effective for immobilizing African lions in Tanzania. Nineteen adult females were given between 55 and 110 mg xylazine hydrochloride in the first dart. Initial doses of 110 mg xylazine hydrochloride and 450 mg ketamine hydrochloride equivalent to greater than 0.9 mg/kg xylazine hydrochloride were most effective in achieving rapid immobilization. Lower doses of xylazine hydrochloride required supplementation with ketamine hydrochloride. These doses could be delivered easily in 3-ml darts. The use of lightweight darts and a blowgun was found to be useful as a supplement to longer range dart projector systems since many animals could be approached at short range.     

Gene flow and immigration: genetic diversity and population structure of lions (Panthera leo) in Hwange National Park,Zimbabwe

The genetic diversity and population structure of a population of African lions in Hwange National Park, Zimbabwe, was studied using 17 microsatellite loci. Spatial genetic analysis using Bayesian methods suggested a weak genetic structure within the population and high levels of gene flow across the study area. We were able to identify a few individuals with aberrant or admixed ancestry, which we interpreted as either immigrants or as descendants thereof. This, together with relatively high genetic diversity, suggests that immigrants from beyond the study area have influenced the genetic structure within the park. We suggest that the levels of genetic diversity and the observed weak structure are indicative of the large and viable Okavango-Hwange population of which our study population is a part. Genetic patterns can also be attributed to still existing high levels of habitat connectivity between protected areas. Given expected increases in human populations and anthropogenic impacts, efforts to identify and maintain existing movement corridors between regional lion populations will be important in retaining the high genetic diversity status of this population. Our results show that understanding existing levels of genetic diversity and genetic connectivity has implications, not only for this lion population, but also for managing large wild populations of carnivores.     

A serosurvey of viral infections in lions (Panthera leo), from Queen Elizabeth National Park, Uganda

Serum samples from 14 lions (Panthera leo) from Queen Elizabeth National Park, Uganda, were collected during 1998 and 1999 to determine infectious disease exposure in this threatened population. Sera were analyzed for antibodies against feline immunodeficiency virus (FIV), feline calicivirus (FCV), feline herpesvirus 1 (feline rhinotracheitis: FHV1), feline/canine parvovirus (FPV/CPV), feline infectious peritonitis virus (feline coronavirus: FIPV), and canine distemper virus (CDV) or for the presence of feline leukemia virus (FeLV) antigens. Ten lions (71%) had antibodies against FIV, 11 (79%) had antibodies against CDV, 11 (79%) had antibodies against FCV, nine (64%) had antibodies against FHV1, and five (36%) had antibodies against FPV. Two of the 11 CDV-seropositive lions were subadults, indicating recent exposure of this population to CDV or a CDV-like virus. No lions had evidence of exposure to FeLV or FIPV. These results indicate that this endangered population has extensive exposure to common feline and canine viruses.     

Estrus behavior and fecal steroid profiles in the Asiatic lion (Panthera leo persica) during natural and gonadotropin-induced estrus

In this paper the behavior of the Asiatic lion was studied during natural and gonadotropin-induced estrus in relation to fecal estradiol and progesterone concentration. The average length of estrus was 5.4 days and no significant difference was observed between natural and gonadotropin-induced estrus. Vocalization and rolling were the major estrus behavioral activities of Asiatic lions and the frequency of these activities were similar in both natural and gonadotropin-induced estrus and treatment with exogenous gonadotropin did not alter estrus behavioral activities. A significant positive correlation was observed between fecal estradiol and frequency of estrus behavior during natural and gonadotropin-induced estrus. Following gonadotropin treatment estrus could be induced in 69% of animals and these induced animals ovulated following hCG treatment. This study reports for the first time the successful use of the non-invasive fecal steroid assay for monitoring the induction of estrus and ovulation in the Asiatic lion.