Landscape Genetics and Habitat Viability of the Estuarine Crocodile in Sabah

Project Description

PhD Candidate: Sai Kerisha Kntayya

Supervisors: Benoit Goossens, Pablo Orozco Ter-Wengel

Institution: Cardiff University

Duration: October 2017 – October 2022


Research questions

  1. To estimate baseline population demographic information of the estuarine crocodile in Sabah using common crocodilian census techniques.
  2. To characterize the spatial ecology of the estuarine crocodile population in Sabah by satellite tracking individuals to determine movement patterns, home range and habitat use.
  3. To characterize the genetic diversity of the estuarine crocodile populations in Sabah using genetic markers.
  4. To determine the influence of landscape structure on the gene flow of estuarine crocodile populations, in Sabah.
  5. To determine extinction vulnerabilities and future population trends of the estuarine crocodile in Sabah using Population Viability Analysis (PVA).


A total of 10 rivers, comprising six districts in Sabah will be surveyed, covering all regions and major river systems in the state that are known to harbor crocodile populations. Historic data from these previous surveys will facilitate population trends identification. Visual encounter surveys will be carried out by boat. Each stretch of river will be surveyed upstream from a motorboat at night for approximately 50km depending on the river. A H14.2 led lenser head torch will be used to identify the red eye shine of crocodiles. Once an individual is spotted, the boat is brought as close as possible to the animal. Once in close proximity to the animal, a GPS location, the habitat category and an estimated size of the animal will be recorded into a data sheet. Other parameters such as density, distance surveyed and river systems will also be recorded. Multiple surveys will be conducted across the rivers, each during the same time of previous years to avoid seasonal bias. Individuals of not more than 70cm in length will be sampled by hand capture. Once secure, a number of morphological parameters will be recorded including total length, snout-vent length, and head length. Weight will be recorded by a spring-balanced weight. Tagging of adult crocodiles for spatial analysis will take place using iridium satellite tags from African Wildlife Tracking (AWT) company providing location fixes and allowing for two-way data communication. During the process of tagging, monomorphic measurements will be taken and a tissue sample will be obtained for genetic analysis.

Expected outcomes, how is this research going to impact the species/habitat

Whilst estuarine crocodile populations in Sabah have recovered following state-wide protection, there have been no studies on the extinction risk of this animal in the context of the rigorous state economic development that will undoubtedly cause future alterations to the landscape. This study is vital due to the recent and escalating occurrences of HCC throughout Sabah, prompting current interest by the state government of Sabah to evaluate the ramifications of a legal harvest. The results of this study will help to reveal whether non-detriment findings (NDF) on the estuarine crocodile population in Sabah can be demonstrated, and consequently provide management plans to establish whether, and subsequently ensure, sustainable utilization and ultimately, the survival of this species.