conservation.arizona.edu - biodiversity

Seasonal flow dynamics exacerbate overlap between artisanal fisheries and imperiled Ganges River dolphins

mmerrick — Mon, 09 Nov 2020 22:51:05 +0000

Authors

Shambhu Paudel

John L. Koprowski

Michael V. Cove

Here we quantify the effects of artisanal fisheries on the ecology of a small cetacean, the Ganges River dolphin (Platanista gangetica gangetica, GRD), in a large river system of Nepal. We examine the size-classes of fisheries’ catches, behavioural changes in GRD in response to fishing activities, and diel overlap between GRD and fishing activity. We observed high human exploitation rates (> 60% of the total catch per effort) of GRD-preferred prey sizes, indicating risks of high resource competition and dietary overlap, especially during the low water season when resource availability is reduced. Competitive interactions in the feeding niches during the low water season, plus temporal overlap between the peak exploitation and critical life-history events (e.g., reproduction), likely have ecological consequences. Furthermore, we detected 48% (95% CI 43–52%) increase in the chance of behavioural changes among dolphins exposed to anthropopressure (fishing activity), risking social behaviour impairment in exposed dolphins. The higher diel overlap and increased diel coefficient as the surveys progressed towards the monsoon season suggest temporal shifts in GRD socio-behavioural states and seasonal effects on resource partitioning, respectively. This work identifies drivers of small cetaceans-fisheries interactions and their consequences, and can be used to help reduce biologically significant fishing impacts on small cetaceans. Mitigation strategies, together with river sanctuary and distanced-based approaches, should be urgently included in a framework of ecosystem-based management.

Additional Information

Scientific Reports

Date of publication:

2020

Topics

Freshwater ecology

Conservation biology

biodiversity

Research Categories

Behavioral Ecology Disturbance Ecology Human Wildlife Conflict Threatened and Endangered Species

Koprowski, J. L. 2005. The response of tree squirrels to fragmentation: A review and synthesis. Animal Conservation 8: 369-376.

thackerk1 — Mon, 22 Jul 2019 23:29:48 +0000

Authors

John L. Koprowski

Habitat fragmentation is often considered a major threat to biodiversity; however, our understanding of how fragmentation impacts populations is poor. Identifying appropriate models for such studies is difficult. Tree squirrels are dependent on mature forests for food, cover and nests; these are habitats that are being fragmented rapidly and that are easily defined by humans. Squirrels represent excellent models for study of fragmentation. The literature on tree squirrels was reviewed to glean data on density and home-range size in forest fragments. Sufficient data were available on four species (Sciurus carolinensis, S. niger, S. vulgaris, Tamiasciurus hudsonicus). Density was negatively related to fragment size for S. carolinensis and S. niger and marginally so for T. hudsonicus. Sciurus vulgaris did not exhibit this relationship. Home-range size was analyzed for three species of Sciurus and was positively related to forest fragment size for S. carolinensis and S. niger. Again, only S. vulgaris did not to show this relationship. Sciurus vulgaris is rarely found in small forest fragments and is believed to be especially sensitive to fragmentation; other tree squirrels appear to be sensitive to fragmentation in more subtle ways. Home range compaction provides a mechanism by which densities may increase in small fragments. The demographic consequences resultant from the high densities of squirrels found in small woodlots are not known but may explain the forest damage, avian nest predation and reduced diversity often cited to occur in woodland fragments.

Additional Information

The response of tree squirrels to fragmentation: a review and synthesis

Date of publication:

2005

Topics

habitat fragmentation

biodiversity

tree squirrels

home range

density

Koprowski, J. L., S. L. Doumas, M. J. Merrick, B. Oleson, E. E. Posthumus, T. G. Jessen, and R. N. Gwinn. 2013. It's lonely at the top: Biodiversity at risk to loss from climate change. In Gottfried, Gerald J.; Ffolliott, Peter F.; Gebow, Brooke S.; Eskew

thackerk1 — Mon, 22 Jul 2019 21:36:58 +0000

Authors

John L. Koprowski

Sandra L. Doumas

Melissa J. Merrick

Brittany Oleson

Erin E. Posthumus

Timothy G. Jessen

R. Nathan Gwinn

Climate change is a serious immediate and long-term threat to wildlife species. State and federal agencies are working with universities and non-government organizations to predict, plan for, and mitigate such uncertainties in the future. Endemic species may be particularly at-risk as climate-induced changes impact their limited geographic ranges. The Madrean Archipelago is characterized by high levels of endemism, natural fragmentation, and increasingly poor connectivity among the mesic montane islands within an arid matrix of low elevation deserts and grasslands. The region already has experienced an increase in temperature and this trend is predicted to accelerate over the remainder of the century. We assessed patterns of elevational distribution of reptiles and mammals within the Madrean Archipelago. We examined incremental temperature increases and determined how much reptilian and mammalian biodiversity is at-risk to be lost from montane islands due to elevational and geographic restriction. We estimate that 15 to 20% of all reptile and mammal diversity is at risk of loss by 2100 based solely on predicted patterns of upslope migration of biotic communities driven primarily by climate change. With this significant proportion of native species, we suggest that this emphasizes the need to continue traditional management actions focused on habitat improvement, restoration and connectivity for the majority of species in combination with innovative and active management strategies directed at the subset that is most at risk of extirpation.

Additional Information

It’s Lonely at the Top: Biodiversity at Risk to Loss from Climate Change

Date of publication:

2013

Topics

climate change

endemic species

geographical range

biodiversity

Madrean Archipelago

restoration

habitat

connectivity