Philippine Crocodile Research Articles

Use of diet and body condition assessments as intermediate indicators of translocation success in the Critically Endangered Philippine crocodile (Crocodylus mindorensis)

AbstractIntermediate metrics of translocation success are useful for long‐lived, slow to mature species where survival and reproduction happen over decades.With fewer than 150 individuals in the wild, the Critically Endangered Philippine crocodile (Crocodylus mindorensis) is one of the most threatened species on Earth. This study presents the first analysis of diet and body condition of wild Philippine crocodiles and headstarted (i.e. captive‐reared) individuals released into the wild over the last decade, and uses these results to show how diet and body condition can be pertinent intermediate metrics of translocation success.Analyses of stomach contents revealed 17 different aquatic and terrestrial invertebrate and vertebrate prey species. Interestingly, 70% of Philippine crocodiles showed snails to be the predominent prey type, followed by fish (36.7%), birds (33.3%) and reptiles (33.3%). More than 50% of crocodiles consumed the invasive golden apple snail, a leading agricultural pest. Regardless of crocodile history (wild vs. headstarted) or size class (juvenile vs. adult), no evidence was found for dietary differences in percentage occurrence, percentage composition or prey diversity.Body condition was significantly higher in wild compared with headstarted individuals when analysed together in a pooled group, although neither group differed significantly from the standardized expectation, and headstarted individuals were not significantly different when body condition was derived independently for the two groups.This study provides a working example of how assessing the convergence of diet and body condition between translocated and wild individuals can provide complementary monitoring parameters to demonstrate post‐release establishment of translocated crocodylians. The congruent dietary composition and comparable body condition observed in this study suggest that headstarted crocodiles adapt well following release.Crocodylus mindorensissurvives in an agricultural landscape and is likely to play an ecologically important role by exploiting invasive species, reinforcing the importance of this species to local communities.

Serum Biochemical Profile of Captive-bred Philippine Crocodiles (Crocodylus mindorensis Schmidt, 1935) Sub-adults

The Philippine crocodiles Crocodylus mindorensis Schmidt, 1935 are a critically endangered species that necessitate minimally invasive diagnostic tools for their physiological state and health assessment. In the current study, we determined the reference ranges for the serum biochemistry of male and female captive-bred C. mindorensis sub-adults. We collected blood samples from the post-occipital venous sinus of six male and seven female captive-bred crocodile sub-adults at the Palawan Wildlife Rescue and Conservation Center and quantified the serum biochemical values for cholesterol, triglycerides, uric acid, glucose, creatinine, aspartate aminotransferase (AST), alanine aminotransferase (ALT), albumin, total protein, and globulin. We defined reference ranges through the central 95% of the concentration values obtained. The uric acid concentrations were significantly different between male and female C. mindorensis sub-adults. Uric acid levels were higher (P = 0.035) in male sub-adults because of their higher food intake resulting from dominance and aggression during feeding times. Serum biochemical values of C. mindorensis exhibited similarities with and variations from other crocodile species. We briefly discussed the differences with other species and the influence of factors such as field and laboratory methodologies, environmental conditions, nutritional status, and size class.

Characterisation of sperm production and morphology in the male Philippine crocodile Crocodylus mindorensis via voluntary behavioural training.

Philippine crocodiles Crocodylus mindorensis are critically endangered due to agricultural and fishing threats that have severely fragmented their habitat and population in the Philippines. Captive management plans are important to safeguard against their extinction, but the current population in US zoos is small, and breeding is hampered by the slow growth of this species and the danger of introducing differently sized animals for breeding. There is little information regarding the sperm characteristics of crocodilians, and none for Philippine crocodiles. In this study, we sought to characterise sperm production in the male Philippine crocodile (n =1) by performing voluntary (without sedation or restraint) collections (n =181) over a 3.5-year period. Peak sperm production in this individual occurs from January to July, when the mean (±s.e.m.) total number of spermatozoa recovered was 10.2×106 ±3.8×106 (n =104), compared with 0.3×106 ±0.2×106 (n =71) for all other months of the year. Analysis of sperm morphology indicated that 15.9% of spermatozoa exhibited normal morphology. A bent tail was the most common abnormality (48.2%) observed. Understanding the basic reproductive biology of the male Philippine crocodile will facilitate the development of artificial reproductive technologies to improve captive propagation and genetic management of this species.

Crocodilians and fisheries in the Philippines: revisiting Fittkau’s hypothesis

Crocodilians have been assumed to influence aquatic primary productivity and fishery yield. However, strong empirical evidence to support such claims is lacking. The long-standing assumption first hypothesized by Fittkau (1970), is that local fisheries (secondary productivity) in areas inhabited by crocodilians would be expected to improve. We tested this hypothesis at two locations in the Philippines, inhabited by the Philippine Crocodile (Crocodylus mindorensis) in Paghungawan Marsh in Siargao Island Protected Landscape & Seascape (SIPLAS), Jaboy, Pilar, Surigao Del Norte, and the Indo-Pacific Crocodile (Crocodylus porosus) in the Rio Tuba River, Bataraza, southern Palawan Island. Water chemistry parameters, with emphasis on nutrient (nitrate and phosphate) levels, were determined using using standard protocols. Catch-per-Unit Effort (CPUE) of gillnets in sites with crocodiles was compared with corresponding control sites without crocodiles. CPUE was higher in areas inhabited by crocodiles, but appeared not to be directly influenced by nutrient levels. Increased fish catches in areas inhabited by crocodiles might be attributed to several factors, such as reduced fishing pressure due to the presence of crocodiles which discouraged the local fishermen to fish intensively. Overall, while fish catch was higher in areas inhabited by crocodiles, it is too early to attribute this to the nutrient output from crocodiles due to several confounding factors. KEYWORDS: estuarine, fish catch, freshwater, nutrient

Anti-HIV-1 Activity of Crocodylus mindorensis Philippine Crocodile Serum in Cell-free and Cell-associated Virus Interactions to Human Peripheral Blood Mononuclear Cells

Anti-HIV-1 Activity of Crocodylus mindorensis Philippine Crocodile Serum in Cell-free and Cell-associated Virus Interactions to Human Peripheral Blood Mononuclear Cells

The curious case of the endemic freshwater crocodile Crocodylus mindorensis as incidental host of marine fish acanthocephalan

We performed the first host-parasite survey of the Philippine crocodile, Crocodylus mindorensis, a critically endangered species for which ecological information is lacking. We collected by gastric lavage samples of the stomach contents of crocodiles (n = 10) residing at the Palawan Wildlife Rescue and Conservation Center in Puerto Princesa, Palawan, Philippines. The only parasite detected was an acanthocephalan, which was identified as Neorhadinorhynchus nudus (n = 68), a parasite typically found in the marine fish species consumed by three crocodile individuals. Given the known hosts of N. nudus, its parasitism of C. mindorensis in captivity is likely established by consumption of marine fish. Our findings have implications for the conservation management of C. mindorensis, particularly in terms of preventing introduction of parasites that could lead to development of infectious disease or alter the fitness of captive animals.

A longitudinal evaluation of the Communication, Education and Public Awareness (CEPA) campaign for the Philippine crocodile Crocodylus mindorensis in northern Luzon, Philippines

The Philippine crocodile Crocodylus mindorensis is Critically Endangered and its range is restricted to a few localities in human‐dominated landscapes. Therefore, the survival of this species in the wild depends strongly on the support of local people. Communication and education are prerequisites for successful in situ conservation. Over a 12 year period, the Mabuwaya Foundation distributed posters, calendars and comic books, organized theatre shows, gave school lectures, facilitated community meetings and established a crocodile rearing station/visitor centre to mobilize local support for the conservation of the Philippine crocodile in the northern Sierra Madre in Luzon. This paper documents changes in people's awareness of and attitudes towards the conservation of the Philippine crocodile, and changes in people's behaviour in ten barangays (villages) in the municipality of San Mariano. Most people living in crocodile habitat now know that the Philippine crocodile is protected by law and support the conservation of the species in the wild. Hunting, the destruction of nests and the use of destructive fishing methods have all significantly declined in these areas. As a result of the integrated conservation programme, the Philippine crocodile population is slowly recovering.

The necessity of genetic screening for proper management of captive crocodile populations based on the examples of Crocodylus suchus and C. mindorensis

Based on sequences of mitochondrial and nuclear genes, we report on a screening of 11 presumed Nile crocodiles from various European zoos, of which five (from four facilities) turned out to be western Nile crocodiles, Crocodylus suchus , the recently resurrected name applied to the western genetic lineage of Crocodylus niloticus sensu lato . We also provide evidence for a pure species-level genetic background of six additional Crocodylus mindorensis from a European zoo facility, a species that is known to hybridise with Crocodylus porosus . Our results are based on a limited number of genetic markers and thus might miss backcrossed hybrid specimens, but they provide an important basis for the establishment of conservation breeding programmes, already in place for C. mindorensis and contemplated for C. suchus . We found evidence for possible genetic admixture between C. suchus and C. niloticus in a specimen found in Lebanon, possibly representing a released captive-bred hybrid. We reiterate the need for such basic genetic screening especially in morphologically cryptic and poorly studied species in the context of ex-situ conservation breeding, to avoid erroneous species identification and overlooking of unknown evolutionary lineages.

Conservation of the Philippine crocodileCrocodylus mindorensis(Schmidt 1935):in situandex situmeasures

The endemic Philippine crocodile Crocodylus mindorensis is one of the most Critically Endangered crocodilian species in the world. Four major captive-breeding programmes for the Philippine crocodile have greatly contributed to our knowledge about the biology and natural history of the species. In situ conservation actions, such as reintroduction, conservation breeding in large semi-wild areas with no supplementary feeding and head-starting programmes, could result in increasing the numbers of extant wild and semi-wild populations. If concerted efforts are directed at in situ and ex situ conservation, and locating quality habitats in which to establish new conservation sites for Philippine crocodiles, the species is likely to become widespread in the next few decades. Conservation measures that address species-specific issues promoting healthy viable populations in natural habitats are presented in this paper.

First observations on the courtship, mating, and nest visit behaviour of the Philippine crocodile (Crocodylus mindorensis) at the Cologne Zoo

The aim of this study was to gain a better understanding of the social and in particular reproductive behaviour of the Critically Endangered Philippine crocodile. Crocodylus mindorensis has been a focus for international conservation breeding measures for about two decades. Since little scientific data have been gathered on the biology and ecology of the species so far, its breeding remains a challenge. In order to identify behavioural patterns that trigger courtship behaviour, and to determine when sociopositive interactions increase and the animals are ready for reproduction, a pair of two adult C. mindorensis at Cologne Zoo was systematically observed between August 2011 and July 2012 for a total of 583 hours. Observations took place using all occurrences recording and scan sampling, focusing on pre-, post- and actual mating behaviour. We present a detailed documentation of copulations with behaviours such as growling, roaring, and bubbling. Bubbling in both sexes was observed prior to copulations and decreased with the end of the mating season, supporting the assumption that it can be referred to as courtship behaviour. Behaviours that indicate the approach of the breeding season, such as approaches to the dividing slide, bubbling and nest building, could be distinguished. Our findings should help to improve breeding efforts under captive husbandry conditions and thus contribute to the conservation breeding of this highly endangered and difficult to keep crocodilian species.

Population genetics implications for the conservation of the Philippine Crocodile Crocodylus mindorensis Schmidt, 1935 (Crocodylia: Crocodylidae)

Limited information is available on the Philippine Crocodile, Crocodylus mindorensis, concerning levels of genetic diversity either relative to other crocodilian species or among populations of the species itself. With only two known extant populations of C. mindorensis remaining, potentially low levels of genetic diversity are a conservation concern. Here, we evaluated 619 putative Philippine Crocodiles using a suite of 11 microsatellite markers, and compared them to four other crocodilian species sample sets. The two remaining populations from the island of Luzon and the island of Mindanao, representing the extremes of the former species’ distribution, appear to be differentiated as a result of genetic drift rather than selection. Both extant populations demonstrate lower genetic diversity and effective population sizes relative to other studied crocodilian species. The 57 C. mindorensis and C. porosus, Saltwater Crocodile, hybrids identified earlier from the Palawan Wildlife Rescue and Conservation Center were revalidated with a suite of 20 microsatellite loci; however, the timing of the event and the prevalence of hybridization in the species had yet to be fully determined. We defined the hybrids as one first cross from a C. porosus female and a C. mindorensis male and 56 C. mindorensis backcross individuals. This hybridization event appears to be confined to the PWRCC collection.

Identification and comparison of modern and fossil crocodilian eggs and eggshell structures

Eggshells from the three extant crocodilian species Crocodylus mindorensis (Philippine Crocodile), Paleosuchus palpebrosus (Cuvier's Smooth-fronted Caiman or Musky Caiman) and Alligator mississippiensis (American Alligator or Common Alligator) were prepared for thin section and scanning electron microscope analyses and are described in order to improve the knowledge on crocodilian eggs anatomy and microstructure, and to find new apomorphies that can be used for identification. Both extant and fossil crocodilian eggs present an ornamentation that vary as anastomo-, ramo- or the here newly described rugosocavate type. The angusticaniculate pore system is a shared character for Crocodylomorpha eggshells and some dinosaurian and avian groups. Previously reported signs of incubated crocodilian eggs were found also on our only fertilised and hatched egg. Paleosuchus palpebrosus presents unique organization and morphology of the three eggshell layers, with a relatively thin middle layer characterised by dense and compact tabular microstructure.

Effects of Different Rearing Strategies and Ages on Levels of Natural Antibodies in Saliva of the Philippine Crocodile

The endemic Philippine crocodile (Crocodylus mindorensis) is a relatively small, critically endangered freshwater crocodile. In a head start program, crocodile hatchlings are caught in the wild, reared in captivity, and released back into the wild after two years. The current study aimed to determine optimal rearing strategies of Philippine crocodile hatchlings, including identification of possible diseases during rearing, and studying the effect of ages on natural antibody (NAb) levels. Thirty Philippine crocodiles were divided into two groups, half were reared with a hiding board, and half without the hiding board. Both groups received three different kinds of diets: meat, shrimp, or a combination of both. Saliva samples of the crocodiles were taken three times over a period of three months to test for NAb levels. Saliva samples were also taken from older crocodiles and crocodiles from different locations. NAb titres were compared to sheep red blood cells. Each time saliva samples were taken, a health check was done. The results showed that crocodiles would prefer the hiding board, and neither housing nor diet could affect the level of NAb titres in saliva. A positive correlation was found between NAb titres and body size, weight and age. Wild hatchlings had higher NAb titres than the hatchlings born in captivity, but the difference diminished with ageing. Five different diseases were found

Status of the Crocodile (Crocodylus porosus, Schneider) Industry in the Philippines

Crocodiles in the Philippines are listed in the Appendix 1 of the Conservation on International Trade of Endangered Species of Wild Fauna and Flora (CITES). But based on the wide distribution of the Crocodylus porosus, a closed-cycle breeding for commercial trade is permitted though the Crocodylus mindorensis is for conservation. The result of the technology transfer program of the Philippine government CITES registered facility pave way for the birth of crocodile farming industry in the Philippines. In 1999, six (6) private commercial farms that successfully passed the stringent evaluation process have pioneered this non-traditional industry on Saltwater Crocodile farming. The coalition of crocodile farmers or the Crocodylus Porosus Philippines Inc. (CPPI) strengthens the sustainable use and management or value-driven conservation of the two crocodile species in the Philippines. CPPI farms have advanced the industry, providing new technology, innovations and facilities in accordance with international standards. Numbers of crocodiles have increase to approximately 25,000 for leather industry. There were about 4,000 C. porosus skins that have been exported from 2008-2012 and projected to have a total of 10,000 skins available for export in the next 5 years. CPPI is also working towards the conservation of two species of crocodile in their natural habitat in southern Philippines. The industry recognized their responsibility to the Filipino people and its future generations. Government support to access more competitive technology, increase social acceptability of crocodile meat as alternative protein source, support for the development of by-products, and increase support for research and conservation is recommended.

Detection of Crocodylus mindorensis x Crocodylus porosus (Crocodylidae) hybrids in a Philippine crocodile systematics analysis

The Philippine crocodile (Crocodylus mindorensis) is considered one of the most endangered of the crocodilian species.Rumors or anecdotal concerns have existed for some time as to the possibility of hybrid individuals existing in a captivecollection under consideration for providing reintroduction candidates; however, visual observations failed to identify sus-pected hybrids. Samples were collected from 619 Philippine crocodiles from several captive facilities and two free-rang-ing populations. Mitochondrial DNA D-loop (601 bp) fragments were sequenced for each crocodile and compared to 28individuals representing ten crocodile species. Among Philippine crocodiles, 48 variable sites (47 parsimony informativesites) were identified, which defined six C. mindorensis haplotypes and one C. porosus-derived haplotype. Data were alsogenerated for a 965 bp fragment of the ND4 subunit gene fragment for two samples of each D-loop haplotype. Amongthem, 91 variable sites (90 parsimony informative site) were identified, which defined three C. mindorensis haplotypesand one C. porosus-derived haplotype. From the nuclear genome, the C-mos gene was successfully amplified for the 388bp partial fragment for all Philippine crocodile samples. Only two variable sites were identified. These sequences werecompared to GenBank sequences for C. porosus. Of the 619 Philippine crocodile samples, 57 samples were found to har-bor D-loop haplotypes identified as C. porosus and 31 of those harbored C-mos mutational sites diagnostic for C. porosusintrogression. All individuals indicating C. mindorensis x C. porosus hybridization were sampled from the Palawan Wildlife Rescue and Conservation Center.

‘Why must we protect crocodiles?’ Explaining the value of the Philippine crocodile to rural communities

What are valid arguments to protect the Philippine crocodile in the wild? And how are we to explain the normative foundations of biodiversity conservation to rural communities in the developing world? Conservationists mainly rely on economic values to justify in situ wildlife conservation. In this article, we argue that these utilitarian reasons are often based on inaccuracies and flawed assumptions. By focusing narrowly on economic incentives, conservationists risk undermining their credibility and obscuring other valid reasons to protect nature. Cultural and intrinsic values can also form a strong motivation for poor people in non-western societies to conserve biodiversity. In the northern Sierra Madre on Luzon, respect for nature, interest in wildlife ecology and pride in the occurrence and conservation of a rare and iconic species proved to be effective incentives to protect the Philippine crocodile.

What Local People Think About Crocodiles

This article challenges several assumptions that have shaped environmental policy in the Philippines. Policy makers assume that people are antagonistic toward conserving crocodiles in the wild and think that the enforcement of environmental legislation in a context of widespread rural poverty is illegitimate and ineffective. They argue that these negative public attitudes can only be transformed by generating revenues for rural communities, for example, through crocodile ranching or ecotourism. Despite the evident failure to conserve crocodiles in the wild, this thinking continues to underpin policy and practice in the Philippines. A community-based conservation project in the northern Sierra Madre on Luzon puts this utilitarian logic in perspective. The project succeeded in transforming hostile attitudes toward crocodiles and mobilized broad societal support for the protection of the Philippine crocodile and its freshwater habitat. Cultural values, such as pride in the occurrence of this rare and iconic species, form an important incentive for people to support the preservation of the species in the wild. These experiences highlight the importance of moving beyond ideological positions in discussions on biodiversity conservation, and enable the design of integrative and innovative solutions to conserve wildlife in human-dominated landscapes.

Assessing the effectiveness of environmental education: mobilizing public support for Philippine crocodile conservation

There is little quantitative data on the cost effectiveness of environmental communication and education efforts. This study evaluates a public awareness campaign for the conservation of the Philippine crocodile in the northern Sierra Madre in terms of outputs, outreach, cognitive and affective outcomes, and impact through a counterfactual comparison. The campaign succeeded in raising awareness on and transforming attitudes toward in situ Philippine crocodile conservation: most people living in close proximity to crocodiles now know that the species is legally protected and support in situ conservation. As a result, crocodiles are no longer purposively killed. Substantial gains can be made in environmental conservation by investing more in communication, education, and public awareness campaigns, particularly in developing countries. Awareness on legislation and pride in the conservation of a rare and iconic species are strong incentives for poor, rural communities to support in situ wildlife conservation.

Two complete mitochondrial genomes of Crocodylus and implications for crocodilians phylogeny

AbstractThe complete mitochondrial (mt) genomes of two crocodilians: Crocodylus palustris and Crocodylus mindorensis, were sequenced in order to examine their gene and genome features. Additionally, we intended to increase the amount of molecular data suitable for phylogenetic analysis. Their gene orders conform to other crocodilians that have been sequenced, except the arrangement of two tRNA genes differ from other vertebrates, showing that the gene order of crocodilians is remarkably conserved. Phylogenetic analyses (maximum likelihood, Bayesian inference) based on the mt protein-coding genes at the nucleotide level were performed among crocodilians for which complete mt genomes were available. The results suggest that the gharial (Gavialis gangeticus) joins the false gharial (Tomistoma schlegelii) on a common branch, that constitutes a sister group to traditional Crocodylidae. In this report, Mecistops cataphractus is evidently most closely related to Osteolaemus tetraspis. They are isolated as sister taxon from the main clades in Crocodylus. Regarding Paleosuchus, it appears as sister group to Caiman within the Alligatoridae. In particular, relationships among species of Crocodylus (true crocodiles) are discussed.

Cross-species amplification of microsatellites in crocodilians: assessment and applications for the future

Microsatellite DNA loci have emerged as the dominant genetic tool for addressing questions associated with genetic diversity in many wildlife species, including crocodilians. Despite their usefulness, their isolation and development can be costly, as well as labour intensive, limiting their wider use in many crocodilian species. In this study, we investigate the cross-species amplification success of 82 existing microsatellites previously isolated for the saltwater crocodile (Crocodylus porosus) in 18 non-target crocodilian species; Alligator sinensis, Caiman crocodylus, Caiman latirostris, Caiman yacare, Melanosuchus niger, Paleosuchus palpebrosus, Crocodylus acutus, Mecistops cataphractus, Crocodylus intermedius, Crocodylus johnstoni, Crocodylus mindorensis, Crocodylus moreletii, Crocodylus niloticus, Crocodylus novaeguineae, Crocodylus palustis, Crocodylus rhombifer, Crocodylus siamensis, and Osteolaemus tetraspis. Our results show a high level of microsatellites cross-amplification making available polymorphic markers for a range of crocodilian species previously lacking informative genetic markers.