Wetland Vegetation Shifts and Their Role in Modulating Mugger Nest Micro-climates

Wetland vegetation plays a crucial yet often overlooked role in shaping the thermal and moisture conditions of crocodilian nesting habitats. At the Bhor Saidan Crocodile Breeding Centre in Haryana, India, noticeable shifts from native emergent macrophytes (Typha angustifolia, Phragmites karka, Cyperus rotundus) to invasive floating plants such as Eichhornia crassipes and Ipomoea aquatica have raised concerns about their effects on Marsh Mugger (Crocodylus palustris) reproduction. This study investigated how these vegetation transitions influence nest micro-climates during two consecutive breeding seasons (2023–2024). Continuous measurements of nest-core temperature, relative humidity, and soil moisture were collected from 48 nests distributed across emergent-dominated, floating-dominated, and mixed vegetation zones. Nests surrounded by emergent vegetation maintained more stable thermal regimes (mean 30.1 ± 1.3°C) and higher humidity (74 ± 4%) compared with floating-dominated sites, which exhibited greater daily thermal fluctuations and reduced moisture retention. Hatchling success correlated positively with emergent vegetation cover (r = 0.71, p < 0.01). These results highlight that the replacement of emergent vegetation by invasive floating weeds can compromise optimal incubation conditions, potentially lowering reproductive success. Conserving and restoring emergent plant assemblages is therefore critical to maintaining micro-climatic stability in nests and safeguarding Marsh Mugger populations under changing climate and habitat pressures.