The Response of Agamid Lizards to Rainforest Fragmentation in the Southern Western Ghats, India
NM Ishwar1, Ravi Chellam1, Ajith Kumar2, BR Noon3
1 Wildlife Institute of India, PO Box 18, Dehradun 248 001, India
2 Salim Ali Centre for Ornithology and Natural History, Coimbatore, 641 108, India
3 Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, CO D 80523, USA
N M Ishwar
Wildlife Institute of India, PO Box 18, Dehradun 248 001
We examine the response of agamid lizards to the fragmentation of their rainfores habitat in the Western Ghats mountains in southern India. The data come from eighteen transects in nearly 400 sq. km of relatively undisturbed and continuou rainforests in the Kalakad-Mundanthurai Tiger Reserve (KMTR), and thirty-thre transects in fourteen rainforest fragments (less than 1 ha to 2,500 ha) in the Anaimalai Hills, which were sampled during 1997-2000. A total of 263 agamid lizards belonging to eight species were recorded in the KMTR and 443 agamid lizards belonging to five species were recorded in the Anaimalai Hills. In the KMTR species richness showed a unimodal distribution with altitude, while the encounter rate showed a sharp linear decline due to the decrease in two most common species,Draco dussumieriand Calotes ellioti. Transects in forest frag ments at lower elevations (700-1200 m) had lower species richness and encounte rates than the KMTR. Comparison of these forest fragments amongst themselves and with the KMTR showed a decline in the abundance of D. dussumieri C. nemericolaand C. grandisquamis in the smaller fragments. Their encounte rates in the forest fragments, however, were better correlated with habitat feature that represented the structural characteristics of the undisturbed forest (highe canopy height, greater canopy cover and the presence of more buttressed trees) than with the area of the fragment. The most common species in the forest frag­ments,C. ellioti,was unaffected by habitat fragmentation.C. rouxiihas benefite from the fragmentation of these forests and has intruded into the smaller and more disturbed fragments. This study shows that there are considerable differences among species in their response to habitat fragmentation, with some species benefiting(C. rouxii), some remaining unaffected(C. ellioti) and others adversely affected (D. dussumieri, C. nemericola and C. grandisquamis). Protection and restoration of forest fragments, many of which are privately owned, is necessary for the conservation of endemic agamid lizards and other arboreal animals.
Ishwar N M, Chellam R, Kumar A, Noon B R. The Response of Agamid Lizards to Rainforest Fragmentation in the Southern Western Ghats, India. Conservat Soc 2003;1:69-86
Ishwar N M, Chellam R, Kumar A, Noon B R. The Response of Agamid Lizards to Rainforest Fragmentation in the Southern Western Ghats, India. Conservat Soc [serial online] 2003 [cited 2020 Jan 19];1:69-86. Available from: http://www.conservationandsociety.org/text.asp?2003/1/2/69/49351
XTENSIVE LOSS AND fragmentation of tropical rainforests in the past several decades have set the stage for an extinction crisis in the near future as remnant fragments undergo further fragmentation and degraded forests shed species more rapidly (Brooks et al. 2002; Laurance et al. 2002; Pimm and Raven 2000; Saunders et al. 1991). Nonetheless, due to the non-linear nature of the extinction curve (Pimm and Raven 2000), the remnant rainforest fragments still harbour a majority of species that occurred in the extensive rainforests of which they were once part (Brooks et al. 1999). The survival of these species, in fact the rainforest ecosystem itself, depends on our ability to manage the rainforests that occur in a highly frag­mented state (Burkey 1995; Saunders et al. 1991). The long-term survival of species in rainforest patches is threatened by the problems faced by small populations (see Soulι 1986) as well as by the progressive changes in macro- and micro-climate (see Saunders et al. 1991). Loss of species from forest fragments have often been examined within the framework of island bio-geography (for example, Brooks et al. 2002). However, species in a community often respond in complex ways to habitat fragmentation: features of the fragment such as area, presence and the extent of clearings, and nature of edge and matrix, and features of the species such as distribution, dispersal ability, area requirements and diet often determine the long-term fate of species (Lauranceet al.2002). Typically, species are more likely to disappear from small fragments, and endemic, resident or habitat specialist species are more likely to disappear than others (Fagan et al. 1999; Laurance et al. 2002; Nally and Brown 2001).
In this article we examine the community structure of agamid lizards in fourteen rainforest fragments and a large continuous rainforest in the southern Western Ghats in order to identify species' differences in response to habitat fragmentation and features of the habitat with which such responses are correlated.
The Western Ghats extend from almost the southern tip of India (8°N) to River Tapti in the north (21°N), over a distance of nearly 1,600 km. This study was con­ducted in two localities, the Kalakad-Mundanthurai Tiger Reserve (KMTR), al­most at the southern tip of the Western Ghats, and the Anaimalai Hills about 300 km further north [Figure 1]. KMTR contains nearly 400 sq. km of relatively undis­turbed and continuous rainforest. Agamid lizards in this area were sampled around three sites; Kannikatti (700 m), Sengaltheri (1,000 m) and Kakachi (1,200 m) which represented the altitudinal and rainfall regimes in the area [Figure 1].
The Anaimalai Hills exemplify the extent of loss and fragmentation that rain forests have undergone in the Western Ghats between 1860 and 1970, initially fo coffee, tea and teak plantations, and later for the construction of a series of re servoirs (Menon and Bawa 1997). Valparai valley in the Anaimalai Hills, wher the study on rainforest fragments was conducted, presently has nearly 180 sq. k of tea and coffee plantation. Most of the rainforest fragments occur in this landscap surrounded largely by tea estates, which have virtually no canopy cover. Thes fragments range in area from less than 1 ha to about 2,500 ha, and occur in a altitudinal range of 700 m to 1,600 m. For sampling agamid lizards, we selecte fourteen rainforest fragments representing the variability in area and other habitat features among the fragments in the study area [Table 1]. While the four largest fragments (180-2,500 ha) were part of the Indira Gandhi Wildlife Sanctuary that surrounds the Valparai valley, ten (all less than 50 ha) were privately owned. Some of the latter were partly under-planted with coffee or cardamom, while some had human settlements close by. Almost all fragments had been selectively logged, but not in the last two decades. The removal of small timber and fuel wood was the major human interference in these forest fragments, especially in the smaller ones since these were closer to human settlements.
The rainforest vegetation in both study sites is primarily that ofCullenia-Mesua- Palaquium association, although Dipterocarpus-Anacolosa forests occur in the lower elevations (less than 800 m) (Pascal 1988). The rainforest in both sites receive about 300 cm of rainfall annually, nearly 80 per cent of it during the south-west monsoon (June to September). The temperature regime is also comparable, ranging between8°C in December to 31°C in March. Based on rainfall and temperature three seasons may be recognised in both sites: the south-west monsoon (June-September), the north-east monsoon (October-January) and the dry season (February-May).
Study Animals
Agamid lizards in the Western Ghats are represented by fourteen species. Five species (Calotes ellioti, C. nemericola, C. grandisquamis, Draco dussumieri and
Otocryptis beddomei)are endemic to the rainforests at lower elevations (less tha 1,700 m), while two (Salea anamallayana and S. horsefieldi) are endemic to th higher elevations. C. andamanensis,a new record from the Western Ghats durin this study, was perhaps erroneously described to be from the Andaman Island (Ishwar and Das 1998). Four species (C. calotes, C. rouxii, Psammophilus blanfor danus andP.dorsalis) are known to occur along the edges of rainforest.C. versi colorandSitana ponticerianaoccur in other vegetation types in the foothills o the Western Ghats and elsewhere in India.
Agamid lizards are primarily arboreal rather than ground dwelling in the rainfor ests of the Western Ghats, and hence were sampled using forest transects. Thes transects, each 250 m in length, were permanently marked at 25 m intervals, an were sampled thrice in each of the three seasons. In the KMTR sampling was car ried out in eighteen transects during 1997-99. Thus, a total 162 transects wer walked. In the Anaimalai Hills sampling was carried out from June 1999 to Ma 2000. A total of thirty-three transects were sampled in fourteen fragments, th number of transects in a fragment being proportional to its area [Table 1].
During sampling, the forest transects were slowly walked by two observer scanning the understorey (tree trunks, herbs and shrubs). The average time take to walk a transect was about 90 minutes. Sightings were generally restricted t 3m on either side of the transect and up to a height of 8 m, since visibility decrease beyond these distances. All reptile sightings were recorded, if necessary afte capturing the animal for identification of species. Several habitat variables repre senting ground cover, vegetation and canopy were measured from 3 m x 3 quadrats at 25m interval in each transect.
The community structure of agamid lizards was examined with reference to thre properties: species richness, abundance and relative species composition, all o which were estimated from the forest transect data. Species richness was estimate as the total number of species recorded from a transect, including all replicates For each forest fragment, species recorded from all transects were pooled. Abun dance for each transect was estimated as the encounter rate, that is, the mea number of animals per 250 m. The mean of all transects gave the encounter rat in a fragment or fragment size class.
Due to the low encounter rates, analysis was done at two levels. Overall en counter rates and individual species encounter rates were examined in relation t habitat variables in fourteen fragments. In order to increase sample sizes while examining the effect of fragment area, the fragments were grouped into four size classes: very large (>200 ha), large (51-200 ha), medium (10-50 ha) and small (<10 ha).
The bivariate correlations of species richness and encounter rates with habitat variables were examined using linear (Pearson correlation coefficient r) and quad­ratic functions. The latter was selected as the best fit only if there was an increase in R2 accompanied by a reduction in probability level compared to the linear fit. A multiple regression was used to examine the combined influence of all habitat variables on species richness and encounter rates. One-way analysis of variance (ANOVA) was used to test for significance of difference among fragment size classes. If the difference was significant, then Scheffe test was used for pair-wise multiple comparisons to determine which pairs were significantly different. Mean has been given along with its standard error as the measure of central tendency. Regression lines are plotted only when the correlation is significant. All analyses were carried out using SPSS Version 8.0 on a Windows 98 platform.
Continuous Rainforests in the KMTR
A total of 314 arboreal reptiles of twenty-two species were recorded from eighteen transects, which were each sampled nine times. Two hundred and sixty-three of these reptiles (84 per cent) were agamid lizards, 16 per cent were snakes, while geckos and skinks accounted for only 4 per cent. Thus, agamid lizards numerically dominated the arboreal reptile community. A total of eight species of agamid lizards were recorded from transects, including C. and amanensis, which is a new record for mainland India.
The encounter rate (the number of animals per 250 m) varied among the eighteen transects considerably, from 0 to 4.33, with a mean of 1.63? 0.38. Overall, the flying lizard D. dussumieri was the most common, with a mean encounter rate of 0.98 + 0.27, followed byC. ellioti(0.43 + 0.12). The other six species (C. calotes, C. nemericola, C. grandisquamis, C. rouxii, C. andamanensis and P. blanfordanus) were relatively rare, their encounter rates varying between 0.01 and 0.07.Psammo­philusblanfordanus and C. rouxii were recorded only from rainforest edges. Thus, D.dussumieri (60.5 per cent, N = 314) and C. ellioti (26.2 per cent) numerically dominated the arboreal reptile community.
Of all habitat variables that we analysed, altitude had an overriding influence on species richness as well as encounter rates [Figure 2a] and [Figure 2b]. While species richness was best explained by a quadratic relation (R2= 0.57,P<0.05), the overall encounter rate was best explained by a linear relation (R2= 0.86, P<0.05). The encounter rates of the two most common species declined sharply with altitude D.dussumieri,R2 = 0.77;C. ellioti,R2= 0.78, P<0.05, Figures 2c and 2d). Both species were not recorded from altitudes <1,100 m. The records of the other species were too few to examine the effect of altitude. In multiple regression none of the other habitat variables had any effect on the species richness or encounter rates of lizards.
Species Richness A total of 549 reptiles, belonging to nineteen species were recorded from thirty-three transects, each of which was sampled nine times. O these, 443 (80.7 per cent) were agamid lizards, seventy (12.8 per cent) snakes thirteen (2.4 per cent) varanids and twenty-three (4.2 per cent) geckos. Here agai agamid lizards numerically dominated the arboreal reptile community. Five specie of agamid lizards were recorded from the transects: C. ellioti, C. nemericola C. grandisquamis, C. rouxii and D. dussumieri. All five species were recorde from only two fragments (Varattuparai I and Manamboli), four species were recorded from four fragments and only two species from three fragments. There was no significant relationship between the number of species and any of the habitat features we recorded [Table 2].
Encounter Rate The encounter rate of agamid lizards varied among transect from 0.56 to 4.33, with a mean of 1.54+0.12 animals per transect (N= 33). Over all,C. elliotihad the highest encounter rate (0.78? 0.07) followed byD. dussumier (0.43 + 0.10), C. nemericola (0.08+0.02), C. grandisquamis (0.13+0.04) an C.rouxii(0.05+ 0.02). Among fragments, the encounter rate of all lizards togethe ranged from 0.56 animals per 250 m (Tata II) to 3.22 (Pannimedu). C. elliotiha the highest encounter rate among species in eleven out of fourteen forest fragment (ranging from 0.22 to 1.44 animals per 250 m); in three fragments D. dussumier had the highest encounter rate (0.75 to 1.78). The other three species had relativel low encounter rates in all fragments, ranging between 0 and 0.56 animals pe 250 m.
The encounter rate of C. nemericola was positively correlated with canop cover and fragment area, that ofC. Grandisquamis with the presence of buttresse trees andC. rouxiinegatively with canopy height [Table 2]. The encounter rate o the most abundant species (C. ellioti) was not significantly correlated with an habitat variable, while that ofD. dussumieri showed a high positive correlation with canopy height and basal area, and a negative correlation with cut basal are compared with other habitat variables (P<0.1 in all cases). The encounter rate o all lizards together was significantly correlated with canopy height, but only poorly with fragment area. However, a quadratic curve gave a better fit (with an increase in r from 0.10 to 0.43), indicating that encounter rates might be non-linearl correlated with fragment area [Figure 3].
The relationship becomes clear when the fragments are divided into four size classes, and encounter rates estimated as the mean of all transects for each class [Table 3]. The overall encounter rate differed significantly among the four fragment size classes (one-way ANOVA, F = 3.49,df = 3,P = 0.03), being highes in the medium-sized class (11-50 ha) and lowest in the small-sized fragment (less than 10 ha). However, differences between pairs of fragment size class were not significant (Scheffe test,P>0.05). As is evident from Figure 3b, the large (51-100 ha) and medium (10-50 ha) fragments had overlapping encounter rates, which were greater than both small (<10 ha) and very large (greater than 200 ha) fragments. Among species, the encounter rates of D. dussumieri and C. rouxii were significantly different among the fragment size classes [Table 3]. The former was significantly more abundant in the medium fragments, while the latter was more abundant in the small ones compared to other fragment size classes (Scheffe test,P<0.05). The abundance of the other three species did not differ among the fragment size classes. However, it is important to note that the mean encounter rates of C. nemericola and C. grandisquamis (both endemic to the rainforest of the Western Ghats) decline from the largest to the smallest fragment [Table 3].
Relative Abundance Out of 443 agamid lizards recorded from all tran­sects together, 233 (52.6 per cent) were C. ellioti. The next most abundant was D. dussumieri with 128 (28.9 per cent), followed by C. grandisquamis (forty­two, 9.5 per cent),C. nemoricola(twenty-four, 5.4 per cent) andC. rouxii(sixteen, 3.6per cent).C. elliotti was the most common species in all fragment size classes, forming 50 to 63.5 per cent of all lizards. The relative abundance of all other species varied considerably among the fragment size classes. D. dussumieri, the second most common species overall, formed only 2.7 per cent of the lizards in the very large fragments, in contrast to 32.6 per cent in the large fragments and 42 per cent in the medium fragments. On the other hand, the relative abundance of C. grandisquamis and C. nemericola declined as the fragments became smaller.
C. rouxii, which was the second most common species in the small fragments, was absent from the largest fragment. The relative abundance of the five species was significantly different among the four fragment size classes (c2 = 126.6,df= 12,P<0.01) due to the higher relative abundance of D. dussumieri in the large and medium fragments, C. grandisquamis and C. nemericola in the largest frag­ments, and C. rouxii in the small fragments.
The Effect of Altitude The number of species and overall encounter rate of agamid lizards were not significantly correlated with the altitude of the transec (r= 0.17 and -0.32 respectively,n = 33,P>0.05, Figures 4a and 4b). However the encounter rate ofD. Dussumieri was negatively correlated with the altitude o the transect (r= -0.47,P<0.01). This was primarily due to the eight transects is the very large fragment (Akkamalaishola), and three transects in a large fragment (Andiparai), which were all above 1,200 m in elevation. When these transect were excluded, there was no correlation between the encounter rate of D. dussu mieriand altitude. The encounter rate ofC. rouxiiwas also negatively correlate with altitude (r= -0.60,P<0.01), being absent from twenty-five transects tha were above 1,000 m in elevation. The encounter rate of C. nemericola was positively, but weakly, correlated with altitude (r= 0.36,P<0.05), while the encounte rates of C. ellioti(r = 0.06, P>0.05) and C. grandisquamis (rs = 0.32,P>0.05 were not correlated with altitude. However, transects greater than 1,200 m i elevation had greater encounter rates of C. nemericola (0.13 + 0.03) and C grandisquamis (0.21 + 0.03) than in transects less than 1,200 m (0.05 + 0.02 an 0.10+0.02,F= 3.97,F= 7.4,P<0.05 respectively).
Comparison between Continuous and Fragmented Forests Although the overal species richness in the KMTR was greater (eight species) than in the Anaimala Hills (five species), the mean number of species in a transect was significantl greater in the latter (3.09? 0.16) than in the former (2.28? 0.36,F= 5.52,P<0.05) This was, however, due to greater species richness in transects greater than 1,20 m in altitude in the Anaimalai Hills (in the largest fragment, Akkamalai, and large fragment, Andiparai, 2.92+ 0.26), compared to similar altitudes in the KMTR primarily around Kakachi (1.00+ 0.46,F= 15.18,P<0.05). There was no differ ence between the two sites in transects less than 1,200 m in altitude (3.30? 0.2 in the KMTR, and 3.19 + 0.21,F = 0.10,P>0.05 in the Anaimalai Hills).
There was no difference in the overall encounter rate between the KMTR (1.6 + 0.38, n = 18 transects) and Anaimalai Hills (1.54 + 0.13, n = 33, F = 0.08 P>0.05). However, the two areas did show crucial differences among transect above and below 1,200 m altitude. At less than 1,200 m, significantly greate overall encounter rate (2.81+ 0.37,n = 10) was recorded in the KMTR than in th Anaimalai Hills (1.68+ 0.18,n= 12,F= 9.85,P<0.01). In contrast, the larges fragment and a large fragment which were greater than 1,200 m in altitude ha greater encounter rates (1.28+ 0.12,n= 11) than transects in similar altitude in the KMTR (0.15 + 0.07,n = 8,F = 48.97, P<0.01). This was largely due to the absence of C. ellioti and D. dussumieri at higher elevations in the KMTR. In the lower altitude, however, D. dussumieri occurred at much greater abundance in the KMTR (1.77 + 0.30) than in the forest fragments (0.64 ? 0.14, F = 14.99 P<0.05). In contrast, C. elliotishowed no significant difference between the two study areas (KMTR 0.77? 0.15; Anaimalai Hills 0.76? 0.08,F = 0.01,P>0.05) The other species occurred too infrequently to make a comparison of their occurrence.
Altitude and Latitude Influence
Altitude and latitude are important determinants of species richness and abundance although their influence may be considerably moderated by local condition (Brown and Lomolino 1998; Gaston 2000). This is also true for reptiles (Fauth e al. 1989; Scott 1976). In the KMTR agamid species richness showed a unimoda distribution with altitude. In fact, such a pattern is also evident in the KMT when all species of arboreal reptiles are included due to the overlap in the distribution of several species at mid-altitude (Ishwar et al. 1998). In contrast, individual species showed a linear decline with increasing altitude as in the case o D.dussumieri and C. ellioti.There were too few sightings of the other species i the KMTR to detect any altitudinal gradient in their abundance. The only sighting of C. andamanensis was from a transect 1,280 m in altitude in the KMTR. Sale anamallyana and S. horsefieldi occur only at elevations greater than 1,500 m where they are the most abundant reptiles (Bhupathy and Kannan 1997; Ishwar unpublished data). Thus, there are some species that are more abundant at higher altitudes.
In the Western Ghats the southernmost hill range where the KMTR is locate has the highest species richness as well as endemism in flowering plants (Ramesh et al. 1997). The latitudinal pattern in the distribution of other taxa is unclear Among agamid lizards, C. and amanensis is the only species confined to the south ernmost latitudes in the Western Ghats. It has not been reported from Anaimala Hills (about 2° north of the KMTR) and Nilgiri Hills (3° north of the KMTR despite intensive surveys (Bhupathy and Kannan 1997).
The encounter rates and their altitudinal variation in the two sites were no consistent among D. dussumieri, C. ellioti, C. grandisquamis and C. nemericola All these species had greater encounter rates in the large and undisturbed fragment in the higher altitudes in the Anaimalai Hills than similar altitude forests in the KMTR. This difference could represent geographic or latitude differences since the two sites are separated by about 300 km, or could be due to differences in climatic conditions. The higher altitude forests in both the sites, however, have similar annual rainfall being south of the Palghat Gap, and similar temperature regimes being in comparable altitudes. Another factor that could be influencing the observed pattern is that populations were sampled at different phases of their population cycles since the sites were sampled one year apart. The lack of an alti tudinal gradient inC. ellioti and a weaker gradient inD. Dussumieri in the Anaimala Hills, unlike in the KMTR, are obviously due to changes in their abundance in the smaller fragments at lower altitudes.
The Effect of Habitat Fragmentation
Due to the altitudinal effect, it is not possible to compare the lizard community in the largest fragment in the Anaimalai Hills (Akkamalai), which is located above 1,200 m with the smaller fragments, all of which are at elevations lower than 1,200 m. A comparison of the lower altitude fragments with similar altitude in the KMTR shows a drastic decline in the encounter rate of the flying lizard D.dussumieri from 1.77 animals/transect to 0.64. Such a decline in abundance is also obvious within the Anaimalai Hills, in fragments less than 10 ha in area (0.18/ 250 m) compared to medium (0.83) and large fragments (0.54). In the fragments the encounter rate of this species was not related with any of the habitat variables that we measured, but the correlation was highest and nearly significant with basal area of trees and canopy height, which are indicators of large canopy trees in the rainforest. Among the agamid lizards in the Western Ghats this species is perhaps the most arboreal as indicated by its gliding habit. It is very likely, there­fore, that the removal of large canopy trees from forest fragments have had an adverse impact on this species by increasing the distance between large trees and greater canopy openings, both of which could affect their foraging, gliding and anti-predatory behaviour. Another way in which the removal of canopy trees could affect lizards is by changing the thermal environment (Vitt et al. 1997).
Unlike in the KMTR where D. dussumieri was the most common lizard forming 60.5 per cent of the community, C.ellioti was the most common species in Anai­malai Hills forming 50 to 63 per cent of the lizards in different fragment size classes. This increase in relative abundance ofC. ellioti, despite there being no difference in the encounter rates of this species between the two sites, was due to the lower encounter rates ofD. dussumieri. In the forest fragments its encounter rate was not significantly correlated with any of the habitat variables and this species is likely to be a habitat generalist. The species is endemic to the Western Ghats, but occurs in dry deciduous, moist deciduous and rainforests. Thus, this species appears to be a ubiquitous one seemingly unaffected by prevailing forest fragmentation in the Anaimalai Hills.
Two species, C. nemoricola and C. grandisquamis, were found in greater abun­dance in the relatively undisturbed largest fragment at higher altitudes than in the KMTR. It is not clear whether this is due to higher altitudes or due to the larger area of the fragment and lack of disturbance. Their abundance was very low in the KMTR forests at both high and low elevations. Both species have been recorded at lower altitudes elsewhere in the Anaimalai Hills (Ishwar, unpublished data). The encounter rate of C. grandisquamis was positively related to the density of buttressed trees, while that ofC. nemoricola was negatively associated with canopy cover, while both were also correlated with the area of the fragment. It is very likely that both species originally occurred at greater densities in the Anaimalai Hills than in the KMTR, and both have been adversely affected by habitat fragmentation.
The intrusion of secondary forest species into remnant patches of primary forest has been documented in many studies (Burkey 1995; Laurance and Yensen 1991 Murcia 1995; Saunders et al. 1991; Terborgh 1992). A typical example of this i the present study isC. rouxii. This species, typically occurring only along rainforest edges in the KMTR, was recorded from several rainforest fragments although these did adjoin dry or moist deciduous forests. Their encounter rate in forest fragments was negatively correlated with canopy height, indicating their preference for disturbed areas. Smaller, more disturbed fragments had greater encounter rate of this species.
This study has demonstrated that endemic agamid lizards continue to survive i rainforest fragments, but that there has been a decline in the abundance of three endemic species due to habitat fragmentation: D. dussumieri, C. nemericola an C.grandisquamis. Although an area effect is evident, their abundances were bette correlated with habitat features that represent undisturbed forests (canopy height canopy cover and buttressed trees). An earlier study in the same area found that the occurrence of two other endemic arboreal species in forest fragments (the lion-tailed macaque, Macaca silenus, and Nilgiri langur, Trachypithecus johnii was also better predicted by canopy height and tree density than by fragment are (Umapathy and Kumar 2000). Thus, protection of forest fragments from further degradation through human activities such as logging and habitat restoration through assisted regeneration of rainforest tree species can considerably enhance the survival of not only arboreal lizards, but also other arboreal animals. However many of the forest fragments in the Western Ghats are under private ownership (corporate bodies and individuals) and have low levels of protection. Therefore protection as well as restoration has to be promoted through education, economic incentives and legislation.[25]
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[Figure 1], [Figure 2a], [Figure 2b], [Figure 3]
[Table 1], [Table 2], [Table 3]
Ishwar N M
Chellam R
Kumar A
Noon B R
Conservation Imp...