1. Introduction
The Javan leopard (
Panthera pardus melas Cuvier, 1809) is a leopard sub-species with a minimal distribution, including only Java Island [
1] and Nusakambangan Island [
2]. The Javan leopard is the apex predator on the island of Java and is a keystone species in the forest ecosystem on the island due to the extinction of the Javan tiger (
Panthera tigris sondaica), and the lack of other carnivorous species with a larger body size than the Javan leopard [
3].
The Javan leopard (
Panthera pardus melas Cuvier, 1809) is a protected animal based on Government Regulation Number 7 of 1999 concerning Protected Plant and Animal Species. According to the International Union for Conservation of Nature and Natural Resources (IUCN), the status of the Javan leopard is critically endangered (critical). The Javan leopard is also included in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) [
4]. The Javan leopard population on Java Island is estimated to have decreased consistently each year [
5]. The number of Javan leopards in the conservation areas on the island of Java is estimated at 350–700 individuals [
6].
Java Island has the largest population in Indonesia (
Figure 1). The forest area, which is the habitat of the Javan leopard, has decreased as the population has increased. The forest area on Java Island in 2020 was 2711.6 ha, a decrease compared to 2019 and 2018 of 2849.6 ha and 3212.6 ha, respectively [
7]. Reduced forest cover can lead to the extinction of plants and animals [
8]. One of the animals affected by the decline in forest area is the Javan leopard. Habitat destruction includes habitat loss and quality degradation, and it is the most significant cause of the extinction of populations and species, especially carnivores [
9].
The habitat of the Javan leopard in western Java is better than that in eastern Java. This is evident from the increased likelihood of Javan leopards being found in areas with higher precipitation [
10]. A study of leopard habitats in India suggested that improved agricultural land, forest, and scrub could increase the area of suitable habitat [
11]. In addition, the suitable leopard habitat in Taman Negara National Park is located 14 km from urban areas [
12]. Information on the spatial data is needed to determine the distribution and habitat of the Javan leopard. Through a spatial analysis, the relationship between the Javan leopard and environmental components can be analyzed so that it can be used as a determinant of the location of suitable habitat for the Javan leopard and determine how much influence each environmental component has on their survival.
It has been estimated that several locations where the Javan leopard is distributed have decreased in quality and suitability. They have abandoned several areas because they are no longer suitable [
5]. This study aimed to (1) identify the habitat suitability for the Javan leopard (
Panthera pardus melas) and analyze the variables that affect the habitat suitability in Java and (2) analyze changes in the suitability of the Javan leopard (
Panthera pardus melas) habitat from 2000 to 2020.
4. Discussion
Ecological niche modeling has been widely used in conservation biology studies. The sampling range and sample size are key factors determining the species distribution model. The habitat suitability model describes the habitat distribution that can support life for a species. In this case, there is a suitable habitat for the Javan leopard on the island of Java. The environmental variables that contributed the most to the model developed here included primary forest, distance from rivers, and settlements.
Primary forest is the variable with the highest contribution. Primary forest is the main habitat for various animals and plants, including the Javan leopard. The Javan leopard prefers mountainous tropical rainforests and lowland tropical rainforests. This is because mountain tropical forests have good vegetation and are rich in species diversity. Lowland tropical forests have quite high species diversity, even though many forests are already secondary, so they are also a good habitat for Javan leopards [
33]. Based on the research by [
10], the distance from the forest is the variable that contributes the most to modeling the suitability of the Javan leopard’s habitat.
Leopards have average home range size ranges of 30–78 km
2 (males) and 23–33 km
2 (females) in protected areas [
34]. In non-protected areas, according to [
35], the range of the male leopard is 6–63 km
2, while that of the female leopard is 6–13 km
2. Based on the presence data overlaid with the forest area, around 10 individuals were found in a forest area of less than 10 km
2, and the rest were found in a forest area of more than 10 km
2. According to [
36], the factor that most affects home range is prey availability. The lower the availability of prey animals, the more the area of the leopard’s home range will increase. The leopard’s home range will be smaller if the population of prey animals is abundant. Distance from the river has a fairly high contribution. Javan leopards can use water sources for hunting prey as many prey animals spend time near water sources due to the higher diversity of vegetation types on the banks of rivers, providing diverse feed types [
37].
Settlement is a variable with a fairly high contribution value in encounters with the Javan leopard. The destruction of the natural habitat of the Javan leopard due to deforestation, land conversion, and fragmentation causes a decrease in carrying capacity, which forces the leopard out of its habitat and into marginal areas in search of food, where they may attack prey such as livestock and target humans as well. As the population density increases, human settlements begin to approach the forest area habitats, often causing the leopards to enter residential areas to hunt livestock. Locating community cattle pens close to forest areas can worsen this problem [
14]. Leopards prefer prey between 25 and 50 kg or less than half their body size, such as goats and poultry [
1]. Based on records from the Javan Leopard Conservation Strategy and Action Plan 2016–2026, during the 2008–2013 period, there were 14 conflicts between leopards and humans due to leopards entering residential areas to prey on livestock. In addition, based on [
38], in 2018–2020, 10 leopard conflicts with humans occurred due to leopards preying on community livestock.
Leopards are a highly adaptable species with an excellent ability to utilize any resources available in human-dominated environments [
39]. According to [
40], Javan leopards live not only in conservation forests but also in production forests. They may also explore plantation areas, such as rubber plantations, tea plantations, and coffee plantations. Leopards often use plantations as trajectories to find prey [
14].
There was a difference in the area between the Javan leopard habitat suitability model in 2000 and 2020. The suitable habitat area in 2000 was larger than in 2020 (
Table 6). This is because the forest, the most suitable habitat for leopards, has been damaged. According to [
41], the forest cover in Java during 2000–2009 reduced by 60.6% due to deforestation. In addition, the increase in settlements to the point where they are close to forests has threatened the habitat of leopards due to human activities.
The reduction in the area of suitable habitat for leopards corresponds to the decline in the leopard population. In 1990, Javan leopards were found in 12 conservation areas, including national parks, nature reserves, and wildlife sanctuaries. These areas supported a total population of 350–700 Javan leopards [
6]. In 2013, a group of Indonesian scientists estimated that there were 491–546 leopards in the remaining natural forests in Java [
42].
Conservation areas are essential habitats for leopards. According to [
33], forests that function as conservation areas generally have the best habitats for wildlife compared to protected forests, production forests, or other land use types. In addition, leopards choose their habitat based on the quality and safety of the forest. Conservation areas have good security for biodiversity because they are far from exploitative human activities and have security patrols High-quality habitats produce more abundant animal life; low-quality habitats will create conditions for populations with low reproductive rates [
15]. Based on the research by [
10], landscapes suitable for the Javan leopard habitat only represent 8.9% of the total area of Java Island.
The unsuitable class of habitat on Java Island has the largest area. This is due to the destruction of forests, leading to the loss of habitat and habitat fragmentation, compounded by hunting for leopards and their prey animals. As the human population on the island of Java has increased, the conversion of land from forests to settlements has increased, reducing the forest area and leading to the isolation of the Javan leopard. The conservation area is an essential habitat for leopards. The quality of the forest in the conservation area has been maintained and has high biodiversity. In addition, the conservation area has a high level of protection from human activities that threaten the life of the Javan leopard.