Spatial dynamics of lions and their prey along an environmental gradient

Establishing the ecological determinants of the spatial dynamics of large African savanna mammals is necessary for understanding the cumulative impacts on the suitability and resilience of their natural habitats, of progressive habitat fragmentation and temporal shifts in climate, fire regimes and elephant browsing. Systematic directional gradients and small‐scale spatial dependence were evident in rainfall, herbivore biomass and lion density in the Masai Mara National Reserve during September 1990 to July 1992. Lion density, the biomass of resident and all herbivore species were autocorrelated within 4.3, 4.1 and 3.3 km, respectively, and peaked in areas of relatively low rainfall but higher microtopographic and vegetation heterogeneity and complexity and more diverse drainage systems. Rainfall influenced herbivore biomass and hence lion density non‐linearly and that influence was apparently modified by forage mineral nutrients, structural habitat complexity, degree of drainage and distance to waterpoints. Lion density was related to the biomass of resident herbivores, even after controlling for rainfall and spatial trends. Persistence of the recent decline in Mara woodlands and increasing human population along the reserve–ranch boundary would likely reduce the reserve's lion population because most lions spent the daytime within the vegetation mosaic fringing drainage lines, away from humans and domestic livestock.     

Lion density and population structure in the Selous Game Reserve: evaluation of hunting quotas and offtake

In 1992, tourist hunting in the Selous Game Reserve generated 1.28 million dollars for the Tanzanian government, of which 0·96 million dollars were returned to wildlife conservation. Lions ( Panthera leo ) are one of three critical species for tourist hunting, consistently generating 12%–13% of hunting revenue from 1988 to 1992. Because of their ecological and economic importance (and intrinsic value), it is important that lion quotas be set so that offtake is sustainable. The population density of lions in Selous ranges from 0·08 to 0·13 adults km⁻², comparable to unhunted ecosystems. The adult sex ratio (36–41% male) and the ratio of cubs to adults (29% cubs) are similar to those of unhunted populations. The ratio of lions to hyaenas is lower in heavily hunted areas (0·17 lions/hyena) than in unhunted areas (0·43 lions/hyena). Hunting levels between 1989 and 1994 took 2·7–4·3% of adult males annually, which is sustainable. The current quota is 10–16% of the adult male population, which exceeds natural mortality rates for male lions. To remain stable if the quota was filled, the population would have to compensate via increased fecundity, increased juvenile survival, or an altered sex‐ratio. Compensation occurs in Selous by producing (or raising) more male than female cubs (66–81% of juveniles are male). Only 28% of the Selous quota was filled in 1992. The percentage of quota filled (both in Selous and nationwide) has dropped since 1988 as quotas have increased. The current intensity of lion hunting in Selous is sustainable, but the quota cannot be filled sustainably.     

Climate and landscape correlates of African lion (Panthera leo) demography

Although many studies have documented aspects of lion ecology, they have generally focused on single sites, leaving broader-scaled factors unanalysed. We assessed range-wide effects of eight biotic and 26 abiotic variables on lion distribution and ecology, based on data compiled from published sources on lion population ecology in 27 protected areas in Africa. Lion pride size and composition were independent of lion density; lion density and home range size were inversely related; and lion density was positively related to rainfall, soil nutrients and annual mean temperature, with some interactive effects between rainfall and soil nutrients. Lion demography was associated most strongly with rainfall, temperature and landscape features. Herbivore biomass and lion density were correlated in univariate regression analyses. However, because herbivore biomass was also related to rainfall and temperature, hierarchical partitioning (HP) allowed us to evaluate independent effects of each variable on lion demography revealing that herbivore biomass had negligible independent contributions. HP indicated that climatic parameters explained 62% of overall variance in demographic parameters, whereas landscape features explained only 32%; climatic parameters were fairly balanced between effects of temperature (34%) and rainfall (28%). Prey (herbivore) biomass is important for lion survival, but its effects appear secondary to environmental factors.     

Crossing to safety: dispersal,colonization and mate choice in evolutionarily distinct populations of Steller sea lions,Eumetopias jubatus

Population growth typically involves range expansion and establishment of new breeding sites, while the opposite occurs during declines. Although density dependence is widely invoked in theoretical studies of emigration and colonization in expanding populations, few empirical studies have documented the mechanisms. Still fewer have documented the direction and mechanisms of individual transfer in declining populations. Here, we screen large numbers of pups sampled on their natal rookeries for variation in mtDNA (n = 1106) and 16 microsatellite loci (n = 588) and show that new Steller sea lion breeding sites did not follow the typical paradigm and were instead colonized by sea lions from both a declining (Endangered) population and an increasing population. Dispersing individuals colonized rookeries in the distributional hiatus between two evolutionarily distinct ( = 0.222,  = 0.053, K = 2) metapopulations recently described as separate subspecies. Hardy–Weinberg, mixed‐stock and relatedness analysis revealed levels of interbreeding on the new rookeries that exclude (i) assortative mating among eastern and western forms, and (ii) inbreeding avoidance as primary motivations for dispersal. Positive and negative density dependence is implicated in both cases of individual transfer. Migration distance limits, and conspecific attraction and performance likely influenced the sequence of rookery colonizations. This study demonstrates that resource limitation may trigger an exodus of breeding animals from declining populations, with substantial impacts on distribution and patterns of genetic variation. It also revealed that this event is rare because colonists dispersed across an evolutionary boundary, suggesting that the causative factors behind recent declines are unusual or of larger magnitude than normally occur.     

Predator and heterospecific stimuli alter behaviour in cattle

Wild and domestic ungulates modify their behaviour in the presence of olfactory and visual cues of predators but investigations have not exposed a domestic species to a series of cues representing various predators and other ungulate herbivores. We used wolf (Canis lupus), mountain lion (Puma concolor), and mule deer (Odocoileus hemionus) stimuli (olfactory and visual), and a control (no stimuli) to experimentally test for differences in behaviour of cattle (Bos taurus) raised in Arizona. We measured (1) vigilance, (2) foraging rates, (3) giving up density (GUD) of high quality foods and (4) time spent in high quality forage locations in response to location of stimuli treatments. In general, we found a consistent pattern in that wolf and deer treatments caused disparate results in all 4 response variables. Wolf stimuli significantly increased cattle vigilance and decreased cattle foraging rates; conversely, deer stimuli significantly increased cattle foraging rate and increased cattle use of high quality forage areas containing stimuli. Mountain lion stimuli did not significantly impact any of the 4 response variables. Our findings suggest that domestic herbivores react to predatory stimuli, can differentiate between stimuli representing two predatory species, and suggest that cattle may reduce antipredatory behaviour when near heterospecifics.     

Do changes in skull size of South American sea lions reflect changes in population density?

Populations of the South American sea lion (SASL, Otaria byronia) have been intensely exploited for leather and oil in different parts of its distribution range throughout the 19th and 20th centuries, generating large changes in abundance. In Patagonia, the SASL population was reduced by more than 90% of its original abundance, and it began to recover after sealing ended. The aim of this work was to assess changes in size and shape of the skull related to changes in population abundance during the last 100 years. Using geometric morphometry techniques, we analyzed 145 individuals (68 males and 77 females) from Patagonia. Skulls were classified by sex, time period (harvest vs. postharvest), and decades of individual's birth. Results indicated that there were differences in skull size but not in shape discriminated by time period. Moreover, individuals of the postharvest period showed a decrease in the skull size during the last two decades, coinciding with the recovery in population abundance. Our results suggest the existence of a density-dependence response in somatic growth of SASL population of Patagonia.     

Phylogeography of lions (Panthera leo ssp.) reveals three distinct taxa and a late Pleistocene reduction in genetic diversity

Lions were the most widespread carnivores in the late Pleistocene, ranging from southern Africa to the southern USA, but little is known about the evolutionary relationships among these Pleistocene populations or the dynamics that led to their extinction. Using ancient DNA techniques, we obtained mitochondrial sequences from 52 individuals sampled across the present and former range of lions. Phylogenetic analysis revealed three distinct clusters: (i) modern lions, Panthera leo ; (ii) extinct Pleistocene cave lions, which formed a homogeneous population extending from Europe across Beringia (Siberia, Alaska and western Canada); and (iii) extinct American lions, which formed a separate population south of the Pleistocene ice sheets. The American lion appears to have become genetically isolated around 340 000 years ago, despite the apparent lack of significant barriers to gene flow with Beringian populations through much of the late Pleistocene. We found potential evidence of a severe population bottleneck in the cave lion during the previous interstadial, sometime after 48 000 years, adding to evidence from bison, mammoths, horses and brown bears that megafaunal populations underwent major genetic alterations throughout the last interstadial, potentially presaging the processes involved in the subsequent end-Pleistocene mass extinctions.     

RANGE-WIDE SURVEY AND ESTIMATION OF TOTAL NUMBER OF STELLER SEA LIONS IN 1989

Abstract: The first range-wide survey of Steller (northern) sea lions ( Eumetopias jubatus ) was completed in 1989 with a total of 68,094 adult and juvenile (nonpup) Steller sea lions counted. This total count includes 10,000 in Russia (15% of the range-wide count), 47,960 in Alaska (70%), 6,109 in British Columbia (9%), 2,261 in Oregon (3%), and 1,764 in California (3%). A range-wide pup count was not obtained. We estimated the 1989 world population based on a calculation for total pups and obtained a range-wide estimate of 116,000 total animals, or about 39–48% of the 240,000-300,000 estimated 30 yr ago.     

Differential Expression of Immune Response Genes in Steller Sea Lions (Eumetopias jubatus): An Indicator of Ecosystem Health?

Characterization of the polygenic and polymorphic features of the Steller sea lion major histocompatibility complex (MHC) provides an ideal window for evaluating immunologic vigor of the population and identifying emergence of new genotypes that reflect ecosystem pressures. MHC genotyping can be used to measure the potential immunologic vigor of a population. However, since ecosystem-induced changes to MHC genotype can be slow to emerge, measurement of differential expression of these genes can potentially provide real-time evidence of immunologic perturbations. MHC DRB genes were cloned and sequenced using peripheral blood mononuclear leukocytes derived from 10 Steller sea lions from Southeast Alaska, Prince William Sound, and the Aleutian Islands. Nine unique DRB gene sequences were represented in each of 10 animals. MHC DRB gene expression was measured in a subset of six sea lions. Although DRB in genomic DNA was identical in all individuals, relative levels of expressed DRB mRNA was highly variable. Selective suppression of MHC DRB genes could be indicative of geographically disparate environmental pressures, thereby serving as an immediate and sensitive indicator of population and ecosystem health.     

Characterization of eight microsatellite loci in Steller sea lions (Eumetopias jubatus)

Steller sea lions (Eumetopias jubatus) are listed as an endangered species in western Alaska and have exhibited a significant population decline throughout their range. Eight microsatellite loci were isolated from genomic DNA libraries. In addition, all these markers were found to be variable in nine individuals of the California sea lion (Zalophus californicus). This panel of markers was developed to analyse population structure in Steller sea lions throughout their range.     

Morphology of the female reproductive organs of the African lion (Panthera leo)

The topography and splanchnology of the reproductive organs of the African lioness were studied and described in situ and after removal. The kidneys were located far caudally in relation to the thirteenth ribs. The suspensory ligament was very well developed, originated in a fan‐like manner from the dorsolateral abdominal wall lateral to the kidney and extended up to a few centimetres cranial to the kidney. The proper ligament of the ovary as well as the round ligament was well developed. The round ligament inserted on the medial femoral fascia. The left ovary was bigger than the right. The ovarian bursa had a short mesosalpinx that did not cover any part of the ovary and the fimbriae extended along the entire length. The urethral tuberculum as well as the urethral crest were well developed. The left uterine horn was longer than the right. The uterine tube was found to open directly into the tip of the uterine horn and not onto a papilla. The reproductive organs of the lioness resembled those of the domestic cat and dog but with some major differences.     

Estimating Abundance of an Unmarked,Low-Density Species using Cameras

Estimating abundance of wildlife populations can be challenging and costly, especially for species that are difficult to detect and that live at low densities, such as cougars (Puma concolor). Remote, motion-sensitive cameras are a relatively efficient monitoring tool, but most abundance estimation techniques using remote cameras rely on some or all of the population being uniquely identifiable. Recently developed methods estimate abundance from encounter rates with remote cameras and do not require identifiable individuals. We used 2 methods, the time-to-event and space-to-event models, to estimate the density of 2 cougar populations in Idaho, USA, over 3 winters from 2016–2019. We concurrently estimated cougar density using the random encounter model (REM), an existing camera-based method for unmarked populations, and genetic spatial capture recapture (SCR), an established method for monitoring cougar populations. In surveys for which we successfully estimated density using the SCR model, the time-to-event estimates were more precise and showed comparable variation between survey years. The space-to-event estimates were less precise than the SCR estimates and were more variable between survey years. Compared to REM, time-to-event was more precise and consistent, and space-to-event was less precise and consistent. Low sample sizes made the space-to-event and SCR models inconsistent from survey to survey, and non-random camera placement may have biased both of the camera-based estimators high. We show that camera-based estimators can perform comparably to existing methods for estimating abundance in unmarked species that live at low densities. With the time- and space-to-event models, managers could use remote cameras to monitor populations of multiple species at broader spatial and temporal scales than existing methods allow. © 2020 The Wildlife Society.     

Threat of rapid extermination of the lion (Panthera leo leo) in Waza National Park,Northern Cameroon

Lion populations in West and Central Africa are small and fragmented. In areas where park management is weak, threats will likely facilitate the extinction of the lion. Wildlife management requires knowledge of the population estimate. The population of lions in Waza National Park (Waza NP) was assessed by individual identification of members in the population. The population was assessed to comprise of 14–21 adult individual lions. The age structure was skewed towards adults; cubs comprised 22% of all lions identified while the sex ratio was 1 : 3. Two out of four collared lions were lost to illegal, retaliatory killings within 1 year; and probably two more males and one more female were also killed during this period. The lion population appears to have declined during the last 5 years with six lions dying per year, which is at a much higher rate than observed in the previous decades. Human‐livestock pressure has increased tremendously in this period, resulting to frequent human‐lion conflicts. To ensure the survival of the lion in Waza NP and in the entire region, management needs to intensify efforts to mitigate the pressure from humans and their livestock.     

Sources of variability in numbers of live births in wild golden lion tamarins (Leontopithecus rosalia)

We examined the effects of several variables on the number of live births in multiparous females in a wild population of golden lion tamarins (Leontopithecus rosalia). Independent variables included the number of infants born to a female the previous breeding season, the number of infants weaned the previous breeding season, the female's age and body mass, the number of adult males and helpers in the group, and the inbreeding coefficient of the offspring. We also tested the hypothesis that trapping and chemical immobilization during pregnancy affected the number of live births. Female body mass was the only statistically significant predictor of the number of live-born infants in the current season when both first and second peaks were included. Characteristics that predicted higher numbers of infants in the first peak of a season were the number of infants born the previous season and the body mass of the female. The greater the number of infants born the previous season, the greater the number of infants born in the first peak of the current season. Factors positively correlated with the number of live births in the second peak within a season included the number of infants born the previous season, as well as the number of available helpers. Due to sample size constraints, the analysis of litters in the second peak did not include body mass of the female as a variable. Inbreeding and handling did not affect the number of live births. We found no evidence that current reproduction negatively impacts future reproduction in this species. We also found no evidence for an age-related reduction in fertility.     

The composition of African lion (Panthera leo) milk collected a few days postpartum

There is very little information on the composition of lion milk. Milk was obtained from all four teats of two African lionesses (Panthera leo) while they were temporarily immobilized; the first lioness was 40 hours postpartum and the second lioness was 10 days postpartum. The lion's milk obtained from the two lionesses in this study contained less solids than reported in literature. The milk of the two females contained, respectively, 192.2 and 166.9 g dry matter/kg milk; 60.2 and 84.6 g protein/kg milk; 113.6 and 136.9 g fat/kg milk; and 68.6 and 77.9 g fat free dry matter/kg milk. Carbohydrate content, analysed only for the first lioness, was 26.5 g lactose/kg milk. These values are much lower than those cited in literature. Electrophoresis and identification of protein bands showed a similar pattern of proteins as seen in cow's milk, but with caseins of less negative charge and whey proteins of smaller molecular size. The milk fat content of the second lioness was higher and varied considerably more among teats. The lipid fraction of lion's milk is characterized by a high content of saturated (palmitic and stearic) and mono-unsaturated (palmitoleic and oleic) fatty acids. Regarding fatty acid composition, lion milk closely resembles human milk. Animal fat plays an important role in the nutrition of African lions. The high fat content of lion milk suggests that the dependency by large predators such as lions on dietary fat is present from birth.     

Influence of colony size on pup fitness and survival in South American sea lions

Increased terrestrial pup mortality in small colonies due to harassment by subadult males has been proposed as a mechanism to explain the stagnation of South American sea lion populations after sealing ended. To test this hypothesis, pup survival rate was assessed in five northern Patagonia colonies with different sizes. Female diet quality as well as pup growth rate and immune status from the largest and smallest of these colonies were also assessed. Results indicated that the pup survival rate increased with colony size and pup‐to‐subadult male ratio. Furthermore, pups grew faster in the smallest colony, although female diet composition and pup immune status did not differ between the two colonies. Inverse relationship between pup growth rate and survival rate indicated that mortality was independent of food supply. In absence of terrestrial predators, infanticide by subadult males is the only mortality source other than starvation and illness and the relationship between pup survival rate and pup‐to‐subadult male ratio approached a type II functional response curve. Thus, infanticide stands as the most likely reason for the observed positive relationship between colony size and pup survival rate, supporting the hypothesis that post‐sealing population stasis was caused by inverse density dependence.     

Characteristics of reproductive biology and proximate factors regulating seasonal breeding in captive golden-headed lion tamarins (Leontopithecus chrysomelas)

Reproduction is highly demanding in terms of energy expenditure, and the costs and benefits associated with postponing or investing in a reproductive effort are crucial determinants of an individual's fitness. Understanding the reproductive potential of a species under varying ecological conditions offers important insights into the dynamics of its social system. This study provides the first detailed analysis of the reproductive potential of wild- and captive-born golden-headed lion tamarins (Leontopithecus chrysomelas) under captive conditions, based on studbook data compiled during 1984-2000. Litters produced by wild-born females breeding in captivity are similar in size to litters observed in the wild, but smaller than litters of captive-born females. The more stringent ecological conditions experienced by wild-born females during maturation may result in a lifelong effect on litter size. However, interbirth intervals are shorter for wild-born than captive-born females. The relatively smaller burden of infant care that results from having smaller litters may allow wild-born females to sustain the next pregnancy sooner. Reproduction in the Brazilian captive population is highly seasonal for both wild-born females and females born in captivity in Brazil. Changes in photoperiod over a year provide a proximate explanation for changes in the proportion of conceptions and births per month. Outside Brazil, breeding occurs year-round, and no clear birth peak is apparent. Information from field reports that could be used to relate this finding to ecological factors, such as resource availability, is unavailable.