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Hot off the Press: Novel Technique to Measure Stress from Turtle Claws


Investigating how stress impacts wild populations, especially in light of huge human-caused changes, is a big question in conservation biology. Does increased urbanization effect stress of animals, and in turn their immune response or reproductive success?

The first step to answering these questions is having a reliable, practical method of measuring long-term stress from wildlife in natural populations. Traditional techniques can involve drawing blood, and requiring this blood to be stored properly in a freezer in the field - a task that can be both invasive to the individual and logistically challenging for many researchers. Also, most methods of measuring stress sample short-term stress by measuring corticosterone (a stress hormone) in blood (capturing days), or hair and faeces (capturing weeks).

For his MSc, James Baxter-Gilbert and his collaborators developed a novel technique of measuring corticosterone from turtle claws! This method is logistically feasible for samplign in the field, as well it capture long-term stress levels (over months or years) in a wild population. Hopefully this method will provide new avenues for research about how stress affects wildlife populations.

Article abstract:

Conservation biology integrates multiple disciplines to expand the ability to identify threats to populations and develop mitigation for these threats. Road ecology is a branch of conservation biology that examines interactions between wildlife and roadways. Although the direct threats of road mortality and habitat fragmentation posed by roads have received much attention, a clear understanding of the indirect physiological effects of roads on wildlife is lacking. Chronic physiological stress can lower immune function, affect reproductive rates and reduce life expectancy; thus, it has the potential to induce long-lasting effects on populations. Reptiles are globally in decline, and roads are known to have negative effects on reptile populations; however, it is unknown whether individual responses to roads and traffic result in chronic stress that creates an additional threat to population viability. We successfully extracted reliable measures of corticosterone (CORT), a known, commonly used biomarker for physiological stress, from claw trimmings from painted turtles (Chrysemys picta) captured at three study sites (road-impacted site, control site and validation site). Corticosterone levels in claws were evaluated as a measure of chronic stress in turtles because CORT is deposited during growth of the claw and could provide an opportunity to examine past long-term stress levels. While male turtles had higher CORT levels on average than females, there was no difference in the level of CORT between the road-impacted and control site, nor was there a relationship between CORT and turtle body condition. In validating a novel approach for non-invasive measurement of long-term CORT levels in a keratinized tissue in wild reptiles, our study provides a new avenue for research in the field of stress physiology.

Reference:

Baxter-Gilbert, J. H., Riley, J. L., Mastromonaco, G. F., Litzgus, J. D., and Lesbarreres. 2014. A novel technique to measure chronic levels of corticosterone in turtles living around a major roadway. Conservation Physiology 2: 1-9.

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#chrysemyspicta #paintedturtle #corticosterone #roadecology #enzymeimmunoassay

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