Research Article: Sridhara, S., Edgaonkar, A., & Kumar, A. (2013). Understorey structure and refuges from predators influence habitat use by a small ungulate, the Indian chevrotain (Moschiola indica) in Western Ghats, India. Ecological Research, 28(3), 427–433.
DOI:10.1007/s11284-013-1031-3

Blog Author: Chandan Kumar Pandey

Key takeaways: 

  • The study is focused on the Indian Chevrotain, a small deer species, to understand the key factors influencing habitat use.
  •  Researchers used pellet groups as indicators of habitat use  across nearly  70 hectares of the least disturbed parts of a tropical rainforest in Someshwara Wildlife Sanctuary.
  • Scientists divided the area into 250 units, each 50 meters by 50 meters, further divided into 4 equal squares. Seventy-three percent of the grids surveyed showed habitat use by the Indian Chevrotain.
  • Results indicated that Indian Chevrotains preferred areas with hiding spots, tree cover, and dense understory while presence of fruiting trees had minimal impact on habitat use.
  • The study shows that apart from stopping hunting, protecting habitat features such as buttress trees and fallen logs that offer hiding spots from predators is important.

 

Picture yourself as one of the tiniest deer residing in a jungle teeming with lethal predators lurking to snatch you as their next meal. In such an environment, every decision about where to dwell or what activities to engage in requires utmost caution. Additionally, considering that smaller deer possess limited digestive capabilities but boast a high metabolic rate, their dietary preferences lean towards easily digestible, sugar-rich foods such as fruits, tender leaves, and fresh grass. Consequently, two primary factors shape the habitat selection of these diminutive deer : the areas of refuge from predators and the abundance of nutritious, easily digestible food sources.

Indian Chevrotain weighs less than 3 kgs and is frequently preyed on by predators. While the IUCN Red List classifies them as “Least Concern,” prior studies have highlighted that these species are often most targeted and hunted by poachers. A research team led by Sachin Sridhara used the Indian Chevrotain, also called Indian mouse deer, as a model species to test the impact of the availability of food and escape cover (features of the habitat that would allow prey to escape a predator) on the habitat use of small deer. For this, researchers used a technique called occupancy modeling. 

Occupancy modeling is a statistical method used to estimate the presence of species in a particular area based on the detection of the species or indirect signs  such as feces, pug marks, etc., at multiple sites or times. It helps researchers understand the distribution and abundance of species, even when direct observation of the animal is challenging or impossible. It further helps scientists to understand how different factors, such as type of habitat or temperature, affect where animals are found. It’s like solving a puzzle: by studying where animals are present and what places they like, scientists can figure out how factors like the environment or human activities impact them.

The study was conducted in Someshwara Wildlife Sanctuary, which spans 88.4 km2, in the Western Ghats mountain range in Karnataka, India. The sanctuary’s altitude ranges from 75 to 870 m, and it receives an annual rainfall of 4,000 mm, primarily during the southwest monsoon from June to September. The research was conducted during the dry period, between December 2009 and April 2010.

Since the Indian chevrotain is cryptic and elusive, in lieu of directly observing the species, researchers employed pellet groups to indicate habitat use. They incorporated spatial replicates into their study design to address the imperfect detection of pellets. Spatial replicates involve collecting data from multiple locations or sites, accounting for variations in habitat conditions and potential biases. Researchers focused on nearly 70 hectares of the least disturbed tropical rainforest within the sanctuary. Using the powerful computation tool QGIS, they meticulously gridded the area into 250 units, each measuring 50 meters by 50 meters, excluding those intersecting with roads and human settlements (46 grids). Each grid was further divided into 4 equal squares whose diagonals formed the four replicates in each grid.  A person then  walked through each grid, scanning the forest floor for pellet groups.  

To understand the impact of habitat characteristics on the habitat use of Indian Chevrotains, researchers measured five variables in each grid. These variables included the number of fruit trees, the count of places providing refuge against predators, an index of understory complexity (USI) based on tree height and ground cover of herbs and shrubs, visibility in the understory (VISIB) determined by a marked rod, and the percentage of canopy cover. Using the occupancy survey framework, the researchers modeled the influence of these variables on habitat use and the probability of detecting Indian Chevrotains. This methodology aims to elucidate the habitat requirements of Indian Chevrotains for conservation and management purposes.

Out of 204 surveyed grids, Indian Chevroatian used  73 % of the grid cells. Among all five variables, only USI significantly affected the probability of the detection of pellets. Similarly, results suggest that Indian Chevroatians used the grids with  more escape cover, to hide from predators present in large numbers. Additionally, the presence of tree cover and dense understory further positively impacted habitat usage by the Indian Chevrotain. However, the presence of fruiting trees did not affect the habitat used by these small deer species. 

The study results provide insight into the ecology of small deer and the factors that can impact their habitat usage.  Extraction of understory forest products like fallen leaves, logs, etc. could further affect the population of small deers like Indian chevrotain. This study shows that protecting the Indian chevrotain involves more than just stopping hunting. It’s also important to keep its habitat safe by preserving features like buttress trees and fallen logs that offer hiding spots from predators. Certain areas, like USI  sites, provide cover and potential food sources and need protection too. The Indian chevrotain’s habitat faces threats from livestock grazing and the removal of fallen logs, leaf litter, and other forest materials. Controlling these activities is crucial. Even though fruiting trees may not seem important in the dry season, they would be vital at other times.

Link to the original article here.

 

Keywords: Indian Chevrotain, Indian mouse deer, Wildlife research, Habitat Use, Small ungulate ecology, Occupancy modeling; Someshwara Wildlife sanctuary.