Adult Tigers Research Articles

Influence of resource gradients and habitat edges on density variation in tiger populations in a multi-use landscape

Spatial heterogeneity in the local densities of terrestrial carnivores is driven by multiple interacting biotic and abiotic factors. Space-use patterns of large carnivores reflect the competing demands of resource selection (e.g., exploitation of habitats with abundant prey) and minimization of risks arising from human interactions. Estimating the relative strength of these drivers is essential to understand spatial variation in densities of large carnivores and there are still key knowledge gaps for many large carnivore populations. To better understand the relative roles of environmental and human drivers of spatial variation in tiger (Panthera tigris) densities, we surveyed a 3000 km2 landscape in North India using camera trap data. Over two years, we photo-captured 92 unique adult tigers. Associating spatial covariates with patterns of detection allowed us to test hypotheses about the relative influence of prey abundance, habitat structure and extent, and proximity to habitat edges on spatial variation in tiger densities across a gradient of anthropogenic disturbance. We documented extensive variation in tiger density within and across management units and protected areas. Spatial variation in prey abundance and proximity to grassland habitats, rather than human use (e.g. extent of human-dominated edge habitat and protection status), explained most of the spatial variation in tiger density in two of the five surveyed sites. The region’s largest tiger population occurred in a multi-use forest beyond protected area boundaries, where wild ungulates were abundant. Our results suggest that tigers can occur at high densities in areas with extensive human use, provided sufficiently high prey densities, and tracts of refuge habitats (eg. areas with dense vegetation with low human use). We argue that tiger conservation portfolio can be expanded across multi-use landscapes with a focus on areas that are adaptively managed as “zones of coexistence” and “refuge habitats”. Advancing this conservation strategy is contingent on greatly strengthening systems to effectively and equitably redress human–wildlife conflict and leveraging existing policies to strengthen local participation in conservation planning and forest stewardship. Our insights into the environmental drivers of spatial heterogeneity in tiger populations can inform both local management and guide to species recovery in working landscapes.

Setting recovery targets for a charismatic species in an iconic protected area complex: The case of tigers (Panthera tigris) in Chitwan–Parsa National Parks, Nepal

AbstractThe Global Tiger Recovery Program has identified enhancing prey populations as a crucial component in achieving its target of doubling wild tiger (Panthera tigris) numbers, as prey density is a key determinant of tiger density. We estimate prey abundance and ecological carrying capacity (ECC) of tigers in the 1579 km2 Chitwan–Parsa source site complex within a globally significant tiger conservation landscape in south‐central Nepal. Surveying 605.1 km of line transects in the Terai plains and Chure hills of Chitwan–Parsa, we estimated an overall density of 55.43 (36.98–83.45) ungulates/km2, and a biomass of 244,630 (151,520–334,270) kg/100 km2 of five abundant ungulates. Chitwan supports 71.58 (49.02–104.71) and Parsa 30.91 (18.70–51.19) ungulates/km2. The prey base can support 177 (119–263) adult tigers based on energetic requirement models. The tiger ECC was ~3.5× higher in Chitwan than in Parsa at a park level. Although opportunities for further recovery of tiger and prey through targeted habitat management exist, the current population of 170 tigers indicates that this population has likely reached its current ECC. We recommend that policymakers and park managers change focus from increasing tiger numbers to developing pre‐emptive conflict mitigation strategies to allow the site to retain the successes it has realized.

Disease threats to tigers and their prey

The contraction of the global tiger population over the last 100 years into small, often isolated subpopulations has made them increasingly vulnerable to the impact of disease. Despite this, the health of wild tigers continues to be insufficiently funded and explored. For example, canine distemper virus (CDV), has been associated with localized declines and increased risk of extinction, and yet has received little research attention in most tiger range countries. The emergence of new pathogenic threats has posed fresh challenges, including African swine fever virus (ASFV), which has the potential to devastate wild boar populations, and severe acute respiratory syndrome coronavirus (SARS-CoV2) with implications for tiger conservation that remain unknown. The objective of this review is to synthesize current research on the health of tigers and their prey that impacts the conservation of tigers in the wild. Published sources are interpreted based on three mechanisms through which disease can affect the viability of tiger populations: (1) by reducing the survival of adult tigers, (2) by reducing breeding productivity, and (3) by reducing the carrying capacity of tiger habitat through decreased prey abundance. Examples of CDV, SARS-CoV2, carnivore protoparvovirus 1 and ASFV are used to illustrate these processes and inform discussion of research and mitigation priorities.

Developmental stage variation in the gut microbiome of South China tigers.

South China tigers (Panthera tigris amoyensis, SC) are the most threatened tiger subspecies in the world. All the living SCs are captive in zoos or reserves and depend on artificial feeding. The composition of the gut microbiome plays an important role in sustaining the health of the host. A comprehensive understanding of the composition and development of the microbial community of SC is helpful to improve the feeding of captive SC. In this study, we collected 47 fecal samples, 37 of which were from SC of three developmental stages, 5 from adult Amur tigers (Am), and 5 from adult Bengal tigers (Bg), which were all housed in the same zoo. We investigated the diversity, richness, and composition of the bacterial microbiomes and we found that the gut microbiome of SC is strongly affected by host aging. The composition of the gut microbiome of juvenile SC experienced dramatic changes from 5 months old to 1 year old, and it showed much less difference when compared to the samples of 1 year old and the subadult. No significant differences were observed between the samples of subadult and the adult groups. The predominant phylum of 5-month-old SC is Fusobacteriota (33.99%) when the juvenile tigers were older than 5 months, and Firmicutes, but not Fusobacteriota, became the predominant phylum of bacteria in their gut. The gut microbiome of SC, Am, and Bg is possibly affected by their genetic variation; however, the core microbiome of these three subspecies is the same. Our data suggest that the gut microbiome of SC undergoes a developmental progression: a developmental phase (cub), a transitional phase (subadult), and a stable phase (adult). These results expand our understanding of the role of age in the development of the gut microbiome of SC.

Density Estimation of Tiger (Panthera tigris) in the Buffer Zone of Corbett Tiger Reserve

Information about how many animals is in an area is essential for designing management strategies for endangered species such as tiger. Due to the tigers’ elusive behaviour, high mobility and occurrence at low densities, it is difficult to determine an unbiased estimate of tiger abundance. To overcome the problem, biologists proposed camera trapping as an effective method to determine the abundance of the tiger. We used camera trapping to determine the abundance and density of the tiger in the buffer zone of the Corbett Tiger Reserve. An effort of 240 trap nights results in the identification of 20 individual adult tigers. Tiger density was estimated at 13.69±3.3 tigers per 100 km 2 . Our estimation of tiger density highlighted the role of the buffer zone in landscape-level conservation of tigers and indicated that buffer zones can support the high density of tigers if appropriately managed. Anthropogenic activities exert enormous pressure on the buffer zone and it is imperative to have holistic management strategies for the long-term conservation of tigers in the human-dominated landscape of Corbett Tiger Reserve.

Conservation potentials and limitations of large carnivores in protected areas: A case study in Northeast China

AbstractProtected areas are considered the cornerstone of endangered wildlife conservation. However, quantified conservation potentials and limitations of large carnivores in protected areas are lacking. In the Northeast Tiger and Leopard National Park (NTLNP) in China, our camera trap survey in 2019 found 26–27 adult Amur tigers and 49–59 adult Amur leopards occurring in the park. Based on spatial area, current prey populations, and environmental carrying capacity of prey, we estimated the supportable number of tigers to be 55, 90, and 101 individuals, respectively. For leopard, these values were 95, 356, and 572, respectively. Further simulations indicated that human land use change scenarios did not contribute much to increasing the potential prey‐supportable populations of Amur tiger and leopard. Our results showed that the number of tigers and leopards in NTLNP is currently low and has a high recovery potential. However, even the highest supportable population is not enough to support the sustainable existence of an Amur tiger population. Therefore, we suggest that, in addition to further restoration and improvement of the prey population and habitat quality in NTLNP, managers should strengthen the connectivity between NTLNP and other habitat patches to form a well‐connected network of protected areas. Promoting the spread of tigers and leopards outwards from this source population in NTLNP through ecological corridor construction would enlarge the area of habitat and is a crucial measure for realizing the sustainable survival of an Amur tiger population in Northeast China.

DETECTION OF VECTOR-BORNE INFECTIONS IN LIONS AND TIGERS AT TWO ZOOS IN TENNESSEE AND OKLAHOMA, USA.

Protozoal and bacterial vector-borne infections are frequently diagnosed in domestic felids. However, with the exception of Mycoplasma haemofelis and Cytauxzoon felis, their occurrence in managed nondomestic felids housed in the United States is largely unknown. Following a case in February 2020 of fulminant cytauxzoonosis in an African lion (Panthera leo), EDTA-whole blood samples were collected opportunistically from February 2020 through June 2020 from 34 adult tigers (Panthera tigris) and eight adult African lions from the same sanctuary in eastern Tennessee as well as 14 adult tigers from a zoo in southern Oklahoma. Samples were analyzed for Cytauxzoon felis, Bartonella spp., hemotropic Mycoplasma, Rickettsia spp., Anaplasma spp., Ehrlichia spp., Babesia spp., and Hepatozoon spp. DNA by PCR amplification. All animals were asymptomatic at the time of collection. None of the Oklahoma animals were positive for vector-borne organisms, but these pathogens were detected in tigers at the Tennessee facility, including Cytauxzoon felis (11.8%), "Candidatus Mycoplasma haemominutum" (5.9%), and Ehrlichia ewingii (2.9%). During the study period, two animals developed clinical signs of cytauxzoonosis and were assessed for vector-borne infections as part of their diagnostic evaluation. This study documents the presence of tick-borne diseases in managed nondomestic felids in the southeastern United States and underscores that ectoparasite control measures should be practiced to minimize exposure of carnivores in managed care.

Keratometry, biometry, and prediction of intraocular lens power in adult tigers (Panthera tigris).

To calculate the necessary pseudophakic intraocular lens (IOL) power to approximate emmetropia in adult tigers. 17 clinically normal adult tigers. 33 eyes of 17 clinically normal adult tigers underwent routine ophthalmic examination and B-scan ultrasonography while anesthetized for unrelated procedures. Specific ultrasound data (globe measurements and corneal curvature) and estimated postoperative IOL positions were utilized to calculate predicted IOL power by use of Retzlaff and Binkhorst theoretical formulas. Applanation tonometry and refraction were also performed. Mean ± SD axial globe length was 29.36 ± 0.82 mm, preoperative anterior chamber depth was 7.00 ± 0.74 mm, and crystalline lens thickness was 8.72 ± 0.56 mm. Mean net refractive error (n = 33 eyes) was +0.27 ± 0.30 diopters (D). By use of the Retzlaff formula, mean predicted IOL power for the postoperative anterior chamber depth (PACD), PACD - 2 mm, and PACD + 2 mm was 43.72 ± 4.84 D, 37.62 ± 4.19 D, and 51.57 ± 5.72 D, respectively. By use of the Binkhorst equation, these values were 45.11 ± 4.91 D, 38.84 ± 4.25 D, and 53.18 ± 5.81 D, respectively. Mean intraocular pressure for all eyes was 14.7 ± 2.69 mm Hg. The calculated tiger IOL was lower than reported values for adult domestic felids. Further studies evaluating actual PACD and pseudophakic refraction would help determine the appropriate IOL power to achieve emmetropia in this species.

Panthera tigris altaica (Carnivora, Felidae) in the Lazovsky State Nature Reserve and in the adjacent non-protected area (Far East of Russia)

To assess the state of the Panthera tigris altaica (hereinafter – tiger) population, its annual monitoring is being carried out on 16 sites within its range, as this subspecies is still considered threatened. These sites include state nature reserves and adjacent territories, which differ in their protection status. In this paper, a number of tiger individuals in groups and reproduction have been compared on these sites to identify factors that determine these parameters. The tiger population in the Lazovsky State Nature Reserve (area of 1210 km2) was compared with the tiger population in an unprotected area (area of 988 km2), which, similarly to the Protected Area, is located on the coast of the Sea of Japan. A description and comparison of these two sites is given. The study has been carried out in 1997–2021 in the Lazovsky State Nature Reserve, and in 1997–2012 in the unprotected site «Lazovsky District». During the winter, information was collected about tiger tracks in the study area, and data on predator tracks were collected out on stationary routes during two field counts. In the Lazovsky State Nature Reserve, the density of routes in various years was 1.0–1.5 km per 10 km2, 1.2 km per 10 km2 in the site «Lazovsky District». Tiger individuals were identified by the width of paw prints. Tracks differed by more than 2 cm were considered belonging to different individuals. Indicators of the tiger population was about twice higher in the Lazovsky State Nature Reserve than in the unprotected site «Lazovsky District». In 1997–2012, in both Lazovsky State Nature Reserve and unprotected site «Lazovsky District», the population density of both adult and subadult tigers was respectively 8.6 ± 0.7 individuals per 1000 km2 and 5.3 ± 0.5 individuals per 1000 km2, while this parameter was respectively 3.1 ± 1.0 individuals per 1000 km2 and 1.7 ± 0.04 individuals per 1000 km2 for tiger cubs younger than a year. The tiger track density in the Lazovsky State Nature Reserve was 3.03 ± 0.51 tracks per 100 km, taking into account the time passed after the snowfalls covering all tracks; on the site «Lazovsky District», this indicator was 1.33 ± 0.27 tracks per 100 km. In 1997–2012, the population density of adults and subadults was significantly (F = 59.40, p < 0.001) higher in the Lazovsky State Nature Reserve than on the site «Lazovsky District». The population density of tiger cubs (F = 6.30, p < 0.018) and the track density (F = 4.86, p < 0.036) were also significantly higher in the Protected Area than in the unprotected one. The survival rate of tiger cubs was also higher in the Lazovsky State Nature Reserve. Here, the proportion of tiger litters with one cub was 16% (n = 4), with two cubs 48% (n = 12), with three 32% (n = 8), and with four 4% (n = 1) of the total number. On the unprotected site «Lazovsky District», the proportion of litters with one cub was 53% (n = 8), with two 27% (n = 4), and with three 20% (n = 3) of the total number. A downward trend in the population density of tiger cubs was found on the site «Lazovsky District». In 2012–2021 in the Lazovsky State Nature Reserve, the average population density was 8.9 ± 1.8 individuals per 1000 km2 for adult and subadult tigers, and 4.3 ± 1.1 individuals per 1000 km2 for tiger cubs, while the average tiger track density was 2.39 ± 0.68 tracks per 100 km. During this period, the population density of tiger cubs decreased in the Protected Area, and there was also a tendency towards a decrease in the relative number of adults and subadults. The regular three-year cycle in the dynamics of the tiger track density in the Lazovsky State Nature Reserve indicates that environmental factors predominantly influence tiger groups here. No regular cycle was observed on the unprotected site «Lazovsky District». This finding and the lower number of tiger individuals in this area are associated with the negative impact of related anthropogenic factors, namely poaching, hunting, and logging. Recreational pressure also affects the tiger groups. In the last decade, the tiger group in the Lazovsky State Nature Reserve has been exposed to anthropogenic factors from the adjacent area. It is concluded that the further protection of the tiger and the increase in its number is possible if Protected Areas of various statuses are established, if extensive buffer zones are created around new and existing Protected Areas, if hunting is prohibited and logging is limited. The use of agricultural lands for other purposes around Protected Areas should be forbidden.

Tiger density, movements, and immigration outside of a tiger source site in Thailand

AbstractLandscape‐scale strategies for conserving wild tigers emphasize the role of core breeding populations (source sites) to replenish surrounding areas which have lost tigers. In Southeast Asia, a few potential source sites remain, particularly Huai Kha Khaeng Wildlife Sanctuary, Thailand (HKK). We investigated tiger density in two reserves (Mae Wong, Khlong Lan: MWKL) adjacent to HKK where tigers and their prey were scarce due to historic poaching but current management offered effective protection. Camera trapping revealed 10 adult tigers (four males, six females), at least two of which had immigrated from HKK. Spatially explicit tiger density was 0.359 tigers/100 km2, 5.6 times lower than HKK. The population was breeding, with six cubs observed. Tiger movements (measured by σ, the spatial scale parameter) were twice as extensive in MWKL as in HKK, indicative of prey scarcity in MWKL. The disparity in density between MWKL and HKK reveals that tiger recovery is a slow process when prey are scarce, even when recovery areas are apparently well‐managed and connected to a source site. We review source‐recovery dynamics of tigers in other sites in Asia and find that low prey impedes landscape‐scale recoveries elsewhere as well.

Comparison of behavioral and cardiopulmonary parameters during immobilization using dexmedetomidine, tiletamine and zolazepam with or without buprenorphine in Siberian tigers (Panthera tigris)

This study compared the effects of the combinations of dexmedetomidine and tiletamine-zolazepam with or without buprenorphine when used for immobilization of Siberian tigers ( Panthera tigris ). Seven adult Siberian tigers with 8.4 ± 3.6 (mean ± SD) years of age and 140.0 ± 55.6 (mean ± SD) kg of estimated weight were recruited. Tigers were administered intramuscular injections of dexmedetomidine (12.0 μg kg –1 ) and tiletamine-zolazepam (1.25 mg kg –1 ) with (DBTZ treatment) or without (DTZ treatment) buprenorphine (0.05 mg kg –1 ). Pulse rate, respiratory rate, rectal temperature, peripheral capillary oxygen saturation and mean noninvasive arterial pressure, and behavioral scores, such as sedation, analgesia, muscle relaxation, posture, and auditory response scores were recorded. The results showed that, although the sedation and analgesia scores were higher in the DBTZ treatment, there were no statistically significant differences in the behavioral scores between the 2 treatments. The DTZ and DBTZ combinations resulted in effective immobilization with similar induction time and quality of recovery. No significant differences in cardiopulmonary effects were observed between the 2 treatments, and the cardiopulmonary parameters remained within biologically acceptable limits. In summary, both DTZ and DBTZ combinations can be used safely and effectively to immobilize Siberian tigers with a smooth recovery from immobilization. This immobilization protocol is appropriate for physical examinations, sample collections and simple surgical procedures on Siberian tigers.

Population structure and spatial distribution of the tiger (Panthera tigris, Felidae, Carnivora) in Southwestern Primorye (Russian Far East)

In 2011–2013, we surveyed the population structure, spatial distribution and the number of tigers in Southwestern Primorye (about 5000 km2). The total number of tigers, according to winter route census, DNA analysis and camera trapping was estimated at 24–25 adults and 6–7 cubs, belonging to four different litters. The location of tigers is mainly confined to areas difficult to access for people, and with a high density of ungulates. Tigers concentrated in the habitat strip bordering China, mainly comprising the 'Land of the Leopard' National Park. A few tiger tracks were recorded outside of protected areas and on hunting tenures.
 Current methods for estimating tiger numbers needs critical reflection. Winter census by tracks in the snow is often largely influenced by subjectivity. The main reason for this is the large number of surveyors of various degrees of qualification and as a result the conflicting interpretation of track identification. In our opinion, the most objective results are obtained from a consistent survey of the territory by a limited number of specialists and daily adjustments of collected materials.
 Precise and informative methods for determining the number and the structure of tiger populations are DNA analysis of biological samples combined with camera trap census. However, a number of significant drawbacks limits their widespread use: this method is labor-intensive and results in high project costs. In addition, weather conditions can greatly affect the preservation of DNA in the samples. There is a need to organize additional survey routes for installing camera traps and detecting of biological samples in order to register the tigresses with young, as they are behavior is often distinguished by a more secretive lifestyle. As a rule, female tigers with young avoid the main movement routes of adult tigers. These methods are expedient only in the smaller survey plots of model areas.

HISTOPLASMOSIS IN NONDOMESTIC FELIDS: A REVIEW OF SIX CASES

One adult leopard (Panthera pardus) and five adult tigers (Panthera tigris) presented with a range of nonspecific clinical signs, including lethargy (6/6), mobility deficits (4/6), and hyporexia (3/6). Hematology and biochemistry revealed a hyperproteinemia characterized by hyperglobulinemia (4/6), hepatocellular enzyme activity increases (3/6), azotemia (3/6), leukocytosis (2/6), hyperbilirubinemia (2/6), or a combination of conditions. Further diagnostics and management varied with the presenting signs and clinicopathological findings, including supportive care, diagnostic imaging, and blastomyces urine antigen analyses. Two animals died, and four were euthanatized. Postmortem findings included granulomatous pneumonia (6/6), fibrinous pleural effusion (3/ 6), pericardial effusion (2/6), and diffuse icterus (1/6). Histopathology revealed round to oval structures with a thin clear wall and purple inclusions within cells of the mononuclear phagocyte system, consistent with Histoplasma capsulatum, in each animal. Disseminated histoplasmosis was found in five cases, with organisms present in the lung (5/5), liver (3/5), lymph nodes (3/5), spleen (2/5), bone marrow (2/5), thyroid (1/5), tongue (1/ 5), kidney (1/5), or a combination of organs. One tiger was found to have pulmonary histoplasmosis without evidence of disseminated infection. On the basis of clinical and pathological findings, histoplasmosis was diagnosed. This case series illustrates the difficulties in antemortem diagnosis of histoplasmosis on the basis of complete blood count, serum biochemistry profile, and antigen testing and underscores that histoplasmosis should be considered a differential diagnosis in any felid presenting with nonspecific clinical signs in endemic areas.

Conservation decision‐making under uncertainty: Identifying when to reintroduce tiger Panthera tigris to Cambodia

AbstractConservationists need to present biological monitoring data to decision makers in a way which clearly represents uncertainty. Providing results in terms of the probability of a hypothesis being true may have greater utility for decision‐making than traditionally used frequentist statistical approaches. Here, we demonstrate such an approach with regard to assessing the suitability of the Cardamom Rainforest Landscape, Cambodia for Panthera tigris (tiger) reintroduction. We estimated the density of tiger prey in the core of the landscape using the Random Encounter Model from camera‐trap data and used Monte Carlo simulation to prorogate uncertainty around our model parameter estimates. This suggests there is currently a low probability that the core area of the landscape supports sufficient prey for a population of 25 adult tigers and that significant prey recovery is thus required prior to any reintroduction into the landscape. The Random Encounter Model contains a number of assumptions and we stress our main purpose is to illustrate an approach to incorporating uncertainty into conservation decision‐making rather than providing robust estimation of current tiger prey densities in the Cardamom Rainforest Landscape. Our approach has wide utility for conveying species monitoring information to conservation planners in a simple to understand fashion.

The spatial distribution and population density of tigers in mountainous terrain of Bhutan

Habitat loss, prey depletion, and direct poaching for the illegal wildlife trade are endangering large carnivores across the globe. Tigers (Panthera tigris) have lost 93% of their historical range and are experiencing rapid population declines. A dominant paradigm of current tiger conservation focuses on conservation of 6% of the presently occupied tiger habitat deemed to be tiger source sites. In Bhutan, little was known about tiger distribution or abundance during the time of such classification, and no part of the country was included in the so-called 6% solution. Here we evaluate whether Bhutan is a potential tiger source site by rigorously estimating tiger density and spatial distribution across the country. We used large scale remote-camera trapping across n = 1129 sites in 2014–2015 to survey all potential tiger range in Bhutan. We estimated 90 individual tigers (60 females) and a mean density of 0.23 adult tigers per 100 km2. Bhutan has significantly higher numbers of tigers than almost all identified source sites in the 6% solution. With low human density and large swaths of forest cover, the landscape of Bhutan and adjacent northeast India is a promising stronghold for tigers and should be prioritized in large-scale conservation efforts.

ECHOCARDIOGRAPHIC PARAMETERS IN EIGHT ADULT TIGERS ( PANTHERA TIGRIS) DURING TWO PHASES OF AN ANESTHETIC PROTOCOL.

Eight adult tigers ( Panthera tigris) underwent a complete echocardiographic examination following sedation with medetomidine, midazolam, and induction of general anesthesia using ketamine and isoflurane (phase 1). Atipamezole was used to antagonize medetomidine (phase 2) and a second echocardiographic examination was performed. Physiologic tricuspid and pulmonic regurgitations were common findings in the sample population and one tiger was excluded from final analyses due to the finding of a ventricular septal defect. Measurements and mean arterial pressure were assessed for statistically significant differences between the two examination phases as well as gender and weight. There was a statistically significant difference between interventricular septum thickness at end systole, ejection fraction, and mean arterial pressure between anesthetic phases while fractional shortening and left ventricular internal dimension at end-systole approached, but did not reach, statistical significance between phases. Weight was found to be a statistically significant predictor of stroke volume and left ventricular internal dimension at end-diastole. The echocardiographic measurements obtained during this study can be used as guidelines for future examinations in adult tigers. The effects of medetomidine on these measurements and systolic function should be taken into account when performing echocardiograms and monitoring anesthetic events.

Elevated potential for intraspecific competition in territorial carnivores occupying fragmented landscapes

The distribution of mammals is determined by a suite of endogenous and exogenous factors. In territorial, polygynous species like tigers (Panthera tigris), males often center their space-use around female territories, repelling competitors from these areas. Competition among males for females leads to increased mortality of both sexes and infanticide of unrelated cubs, which can lead to population declines. We hypothesized that increased territorial overlap among adult male tigers and elevated levels of inter and intra-sex competition would be manifest in populations with male-biased adult sex ratios (ASR). We also assessed whether inter-sex variation in adult survival or degree of habitat connectivity resulted in skewed ASR. We evaluated these hypotheses using camera trap data from three tiger populations occupying habitat patches with varying levels of connectivity and ASRs. Data were analyzed using multi-state occupancy models, where states were defined as habitat use by one or more male tigers in sites with and without female use. As predicted, in populations with male-biased or even ASR we found evidence for increased spatial overlap between male tigers, particularly pronounced in areas adjacent to female territories. Given parity in adult survival, habitat fragmentation likely caused male-biased ASR. Our results suggest that the persistence of small tiger populations in habitat patches with male-biased ASR may be significantly compromised by behavior-mediated endogenous demographic processes that are often overlooked. In habitat fragments with pronounced male biased ASR, population recovery of territorial carnivores may require timely supplementation of individuals to compensate for population losses from intraspecific competition.

Use of plethysmographic variability index and perfusion index to evaluate changes in arterial blood pressure in anesthetized tigers (Panthera tigris).

OBJECTIVE To investigate use of the plethysmographic variability index (PVI) and perfusion index (PI) for evaluating changes in arterial blood pressure in anesthetized tigers (Panthera tigris). ANIMALS 8 adult tigers. PROCEDURES Each tiger was anesthetized once with a combination of ketamine, midazolam, medetomidine, and isoflurane. Anesthetic monitoring included assessment of PI, PVI, direct blood pressure measurements, anesthetic gas concentrations, esophageal temperature, and results of capnography and ECG. Mean arterial blood pressure (MAP) was maintained for at least 20 minutes at each of the following blood pressure conditions: hypotensive (MAP = 50 ± 5 mm Hg), normotensive (MAP = 70 ± 5 mm Hg), and hypertensive (MAP = 90 ± 5 mm Hg). Arterial blood gas analysis was performed at the beginning of anesthesia and at each blood pressure condition. RESULTS Mean ± SD PI values were 1.82 ± 2.38%, 1.17 ± 0.77%, and 1.71 ± 1.51% and mean PVI values were 16.00 ± 5.07%, 10.44 ± 3.55%, and 8.17 ± 3.49% for hypotensive, normotensive, and hypertensive conditions, respectively. The PI values did not differ significantly among blood pressure conditions. The PVI value for the hypotensive condition differed significantly from values for the normotensive and hypertensive conditions. The PVI values were significantly correlated with MAP (r = -0.657). The OR of hypotension to nonhypotension for PVI values ≥ 18% was 43.6. CONCLUSIONS AND CLINICAL RELEVANCE PVI was a clinically applicable variable determined by use of noninvasive methods in anesthetized tigers. Values of PVI ≥ 18% may indicate hypotension.

Pharmacokinetics of ketamine and norketamine following intramuscular administration combined with ketamine in tigers (Panthera tigris)

In zoo practice, for physical examination or medical procedure in captive tigers, chemical immobilization is needed and ketamine (KET) in association with sedatives is an option frequently used (Clark-Price et al., 2015). Aims of the study is the assessment of the pharmacokinetics of KET and its main metabolite, norketamine (NORKET), after its intramuscular administration in combination with dexmedetomidine in tigers.Nineteen adult captive tigers, from different zoos, were scheduled for periodic physical examination or diagnostic procedures at the Milan University facilities. All animals were administered with a combination of KET at 2 mg/kg and dexmedetomidine at 10 µg/kg, given intramuscularly through blowpipe darts. If necessary, tigers where re-administered with variable doses of KET and dexmedetomidine or other drugs. When animals were sufficiently sedated, blood samples were collected every 5-10 min for the time tigers were safely approachable. Nine animals were assigned to standard protocol group (KET 2 mg/kg and dexmedetomidine 10 µg/kg) and ten animals to non-standard protocol group (tigers administered with different doses of KET, 2 – 2.5 mg/kg, and dexmedetomidine 10 – 30 µg/kg or with any other necessary drug, such as titrate-to-effect propofol and isoflurane, respectively for anaesthesia induction and maintenance). Ketamine and NORKET were extracted from plasma according to a validated HPLC-UV method (Zonca et al., 2012). For pharmacokinetic assessment, KET and NORKET concentrations were analysed with a noncompartmental approach (Phoenix® 7.0, Pharsight). Differences in the pharmacokinetic parameters between groups were statistically analysed (SPSS 25.0, SPSS Inc.).This is the first study that evaluates the pharmacokinetics of KET and NORKET in tigers. Due to the harmful attitude of these animals, samples collection was limited to the period of sedation, a short time for a complete pharmacokinetic evaluation. Nevertheless, we observed a favorable kinetic profile of KET and NORKET and, from a clinical point of view, all animals showed a good recovery, no adverse effects and a good level of sedation. Standard Protocol (mean ± s.d.)Non-Standard protocol (mean ± s.d.) KetamineHL_Lambda_zmin77.62 ± 54.5076.14 ± 67.32 Tmaxmin27.78 ± 7.9049.70 ± 29.64 Cmaxug/mL0.63 ± 0.170.67 ± 0.19 AUClastmin*ug/mL23.84 ±6.40*35.97 ± 12.84* AUMClastmin*min*ug/mL802.24 ± 331.03*2054.97 ± 1018.88* MRTlastmin32.88 ± 5.71*54.38 ± 19.71* NorketamineTmaxmin51.89 ± 8.95*77.10 ± 24.41* Cmaxug/mL0.24 ± 0.070.23 ± 0.09 AUClastmin*ug/mL7.30 ± 3.9811.07 ± 5.46 AUMClastmin*min*ug/mL291.94 ± 227.01*701.87 ± 424.80* MRTlastmin36.95 ± 7.32*58.65 ± 19.58*HL_Lambda_z = Elimination Half-Life; Tmax = Time to Maximum concentration; Cmax = Maximum Concentration; AUClast = Area Under the Curve to the last concentration; AUMClast = Area under the first Moment Curve to the last concentration ;MRTlast = Mean Residence Time to the last concentration Tab.1: Pharmacokinetic parameters of ketamine and norketamine in nineteen adult captive tigers after intramuscular administration of 2 mg/kg of ketamine, with or without variation from the standard protocol, in combination with dexmedetomidine (with * are indicated results with p < 0.05).

Gross anatomy of scapula in Tiger (Panthera tigris)

The present study was conducted on the scapula of five adult tigers to record the characteristic features of scapula bone. It was placed on lateral aspect of thorax, directed downward and forward. It was in the form of wide plate having scapular spine on lateral aspect. The height of spine increased gradually towards the distal end. The acromian process was subdivided into hamate process and suprahamate process. Hamate process overhanged the glenoid cavity. The suprahamate process was in the form of thin triangular plate directed backwards. The supraspinous fossa presented undulating surface in its middle. The infraspinous fossa was triangular and more or less flattened. Subscapular fossa was shallow and presented two prominent ridges. The caudal angle of the scapula was terminated in to glenoid cavity which was oval to quadrangular in shape. Cranial and proximal to the glenoid cavity prominent supraglenoid tubercle was observed which had hook shaped coracoid process. Scapula of both the sides were morphologically similar but the morphometrical values for the right scapula were non-significantly higher than the left counterpart (t less than 0.05), which may be of some biomechanical importance.