Ecological and anthropogenic covariates ... - GANGAPEDIA

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gharial, within my study area. Gharial encounter rates and habitat-usage were higher in areas where large sandy banks were adjacent to deep pools of water, indicating that such locations were favoured for basking. I observed that gharial aggregations tend to cluster at sites which had greater water depth – channel width profile. Further, all anthropogenic activities like sand mining, bankside cultivation, human and livestock presence, fishing and people crossing the river, had a negative impact on gharials using an area. This pattern of habitat use was seen consistently in observations across all occasions. Gharial encounter rates and site occupancy were expected to be influenced by seasonality of river discharge and temperature, both of which showed marked changes across the duration of the study. Ambient air and water temperature increased from February to May, and river flow and discharge showed a decrease during this period. In a comparison of gharial counts across the 4 sampling occasions, we see a peak in February, followed by similar relative abundances in March, April and May, assuming closure and detection did not change. February is a period of intensive basking frequency, due to low temperatures, and this greatly increases detection of gharials. This period also coincides with the aggregation of large gharials for breeding. We also see similar relative abundances in March, April and May. However, marked changes in river discharge and temperature within the same period imply that factors other than discharge and temperature are influencing gharial encounter rates in this period. This indicates that other variables may be influencing spatial distribution of gharials along the river stretch at different periods. Site- specificity may also suggest the influence of a combination of these variables on gharial habitat use and preference. 33
Tucker et al. (1997) report that primary change in habitat use was related to maturity status, evident by the habitat differences between immature and adult Crocodylus johnstoni. When water levels subside, crocodiles become restricted to the available aquatic habitats and social interactions become more frequent, particularly during mating and breeding seasons. Divergent foraging patterns, intraspecific behavioural interactions, thermal preference, predator avoidance or social displacement are known to influence habitat associations in crocodilians (Tucker et al 1997). Decreasing water levels, through the dry season, was expected to cause increased clustering of individuals, within the deeper sections of the river. However, this did not manifest during the course of this study, probably because the dry season – reduced flow pattern had already set in at the start of the study and the clustering of gharials observed on all 4 occasions was an artefact of gharial response to reduced flow regimes. However, water levels and discharge are critical factors that are regarded to be the key driver of river and floodplain wetland ecosystems, and hence need to be monitored continually, across different seasons. Also, low water levels lead to increased anthropogenic disturbances, especially along shallow stretches (pers. obs.). Higher incidences of river-crossing and sand mining at these sites were observed. Large scale nest predation (of turtles, skimmers, black-bellied terns, etc) was observed following reduced water levels, and easy access to mid-river islands and sand-spits. Human induced disturbances were seen to have tangible impacts on the spatial distribution of gharials along the river. The presence of people at a site was seen to have a negative impact on gharials using the area. Segments which had people presence, recorded much lower gharial numbers. I observed that gharials took evasive action and submerged themselves when they spotted people, even as far as 200m away. They were seen to be particularly affected by the presence of people if they 34
Page 1 and 2: Ecological and anthropogenic covari
Page 3 and 4: variable data like river discharge,
Page 5 and 6: Table of Contents EXECUTIVE SUMMARY
Page 7 and 8: In the face of increasing proposals
Page 9 and 10: Chapter 1 Ecological and Anthropoge
Page 11 and 12: Introduction Humans live disproport
Page 13 and 14: Despite the release of over 5000 yo
Page 15 and 16: its 523 km run, the river passes th
Page 17 and 18: sites considered favourble based on
Page 19 and 20: correction factor for the float mea
Page 21 and 22: Variable (type) Measurement Details
Page 23 and 24: interpolation deriving from regiona
Page 25 and 26: the effects of covariates measured
Page 27 and 28: We compared Zero-Inflated Poisson (
Page 29 and 30: Assessing changes in habitat availa
Page 31 and 32: Figure 6: Box-and-whiskers plots co
Page 33 and 34: Occasion 1: Residual mean deviance
Page 35 and 36: Occasion 3: Residual mean deviance:
Page 37: Discussion Humans have preferential
Page 41 and 42: once caught in the net are wary of
Page 43 and 44: Bustard, HR and LAK Singh. 1977. St
Page 45 and 46: Hutton, J. 1989. Movements, home ra
Page 47 and 48: Oliver, M.A., R. Webster. 1990. Kri
Page 49 and 50: Chapter 2 Photographic identificati
Page 51 and 52: Hussain, 2009); and is especially a
Page 53 and 54: data also enables the estimation of
Page 55 and 56: A 600km stretch of the Chambal Rive
Page 57 and 58: Marked animals were accorded no exc
Page 59 and 60: Single-crested region Figure 2: Lat
Page 61 and 62: A B C Capture: 07.02.2010 Figure 1.
Page 63 and 64: (Nichols, 1992). Since gharials are
Page 65 and 66: and Ross, JP. 2007. Gavialis ganget
Page 67 and 68: Mazzoil M., McCulloch S.D., Defran
Page 69 and 70: GENERAL CONCLUSION Humans have pref
Page 71 and 72: APPENDIX - 1 Figure 1: Scatter plot
Page 73 and 74: Figure 2: Scatter plots representin

Ecological and anthropogenic covariates ... - GANGAPEDIA

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