Instructor: Steven Clark Clark Community College sclark@clark.edu
Abstract from an article about frogs (genus Rana or Bufo) and trematodes:
We used high-speed videography of staged encounters between tadpoles of either Bufo americanus Holbrook, 1836 or Rana sylvatica LeConte, 1825 and Echinostoma Rudolphi, 1809 cercariae to understand why echinostomatoid trematodes, such as species from the genera Echinostoma and Ribeiroia Travassos, 1939 (implicated in anuran limb deformities), attack specific anatomical regions of tadpoles. Bufo and Rana tadpoles can shed cercariae on their skin from some parts of their body more easily than others. In particular, cercariae that enter the "dead-water zone" at the junction of a tadpole's body and tail appear particularly difficult for tadpoles to brush off. Cercariae that reach this recess can easily enter the inguinal region of tadpoles (as do Ribeiroia spp.) or ascend the tadpole's cloaca (as do Echinostoma spp.). When tadpoles sense cercariae contacting their skin they make explosive movements to shed those parasites. Factors that reduce tadpoles' activity, such as predator threat or certain pesticides, may increase a tadpole's susceptibility to echinostomatoid infection. Because Bufo tadpoles are unpalatable to many predators, they can afford to make more conspicuous evasive maneuvers than Rana tadpoles, and do so in the laboratory. Bufo tadpoles in the field also have a lower rate and different anatomical distribution pattern of Ribeiroia infection than Rana tadpoles. Factors that reduce tadpole activity in the field may act synergistically to increase parasite loads and subsequent deformities in anurans.
Source: Christopher N Taylor, Kerri L Oseen, Richard J Wassersug. Canadian Journal of Zoology. Ottawa: May 2004. Vol. 82, Iss. 5; p. 701 (6 pages)
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Abstract from an article about snow leopards and domestic herds:
Livestock predation by large carnivores and their retaliatory persecution by pastoralists are worldwide conservation concerns. Poor understanding of the ecological and social underpinnings of this human-wildlife conflict hampers effective conflict management programs. The endangered snow leopard Uncia uncia is involved in conflict with people across its mountainous range in South and Central Asia, where pastoralism is the predominant land use, and is widely persecuted in retaliation. We examined human-snow leopard conflict at two sites in the Spiti region of the Indian Trans-Himalaya, where livestock outnumber wild ungulates, and the conflict is acute. We quantified the snow leopard's dependence on livestock by assessing its diet in two sites that differed in the relative abundance of livestock and wild ungulates. We also surveyed the indigenous Buddhist community's attitudes towards the snow leopard in these two sites. Our results show a relatively high dependence of snow leopards on livestock. A higher proportion of the snow leopard's diet (58%) was livestock in the area with higher livestock (29.7 animals km-2) and lower wild ungulate abundance (2.1-3.1 bharal Pseudois nayaur km-2), compared with 40% of diet in the area with relatively lower livestock (13.9 km-2) and higher wild ungulate abundance (4.5-7.8 ibex Capra ibex km-2). We found that the community experiencing greater levels of livestock losses was comparatively more tolerant towards the snow leopard. This discrepancy is explained by the presence of a conservation-incentive program at the site, and by differences in economic roles of livestock between these two communities. The former is more dependent on cash crops as a source of income while the latter is more dependent on livestock, and thereby less tolerant of the snow leopard. These data have implications for conflict management strategies. They indicate that the relative densities of livestock and wild prey may be reasonable predictors of the extent of predation by the snow leopard. However, this by itself is not an adequate measure of the intensity of conflict even in apparently similar cultural settings.
Source: S Bagchi, C Mishra. Journal of Zoology. London: Mar 2006. Vol. 268, Iss. 3; p. 217