Crowding Affects Health, Growth, and Behavior in Headstart Pens for Agassiz's Desert Tortoise

Crowding Affects Health, Growth, and Behavior in Headstart Pens for Agassiz's Desert Tortoise AbstractWorldwide, scientists have headstarted threatened and endangered reptiles to augment depleted populations. Not all efforts have been successful. For the threatened Agassiz's desert tortoise (Gopherus agassizii), one challenge to recovery is poor recruitment of juveniles into adult populations, and this is being addressed through headstart programs. We evaluated 8 cohorts of juvenile desert tortoises from 1 to 8 yrs old in a headstart program at Edwards Air Force Base, California, for health, behavior, and growth. We also examined capacities of the headstart pens. Of 148 juveniles evaluated for health, 99.3 were below a prime condition index; 14.9 were lethargic and unresponsive; 59.5 had protruding spinal columns and associated concave scutes; 29.1 had evidence of ant bites; and 14.2 had moderate to severe injuries to limbs or shell. Lifetime growth rates for juveniles 18 yrs of age were approximately two times less than growth rates reported for wild populations. Tortoises in older cohorts had higher growth rates, and models indicated that high density in pens and burrow sharing negatively affected growth rates. Densities of tortoises in pens (2052042/ha) were 3503500 times higher than the average density recorded in the wild (<1/ha) for tortoises of similar sizes. The predominant forage species available to juveniles were alien annual grasses, which are nutritionally inadequate for growth. We conclude that the headstart pens were of inadequate size, likely contained too few shelters, and lacked the necessary biomass of preferred forbs to sustain the existing population. Additional factors to consider for future reptilian headstart pens include vegetative cover, food sources, soil seed banks, and soil composition. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Chelonian Conservation and Biology Allen Press

Crowding Affects Health, Growth, and Behavior in Headstart Pens for Agassiz's Desert Tortoise

Loading next page...
 
/lp/allen_press/crowding-affects-health-growth-and-behavior-in-headstart-pens-for-8OjbiZ5p9n
Publisher
Allen Press
Copyright
2018 Chelonian Research Foundation
ISSN
1071-8443
D.O.I.
10.2744/CCB-1248.1
Publisher site
See Article on Publisher Site

Abstract

AbstractWorldwide, scientists have headstarted threatened and endangered reptiles to augment depleted populations. Not all efforts have been successful. For the threatened Agassiz's desert tortoise (Gopherus agassizii), one challenge to recovery is poor recruitment of juveniles into adult populations, and this is being addressed through headstart programs. We evaluated 8 cohorts of juvenile desert tortoises from 1 to 8 yrs old in a headstart program at Edwards Air Force Base, California, for health, behavior, and growth. We also examined capacities of the headstart pens. Of 148 juveniles evaluated for health, 99.3 were below a prime condition index; 14.9 were lethargic and unresponsive; 59.5 had protruding spinal columns and associated concave scutes; 29.1 had evidence of ant bites; and 14.2 had moderate to severe injuries to limbs or shell. Lifetime growth rates for juveniles 18 yrs of age were approximately two times less than growth rates reported for wild populations. Tortoises in older cohorts had higher growth rates, and models indicated that high density in pens and burrow sharing negatively affected growth rates. Densities of tortoises in pens (2052042/ha) were 3503500 times higher than the average density recorded in the wild (<1/ha) for tortoises of similar sizes. The predominant forage species available to juveniles were alien annual grasses, which are nutritionally inadequate for growth. We conclude that the headstart pens were of inadequate size, likely contained too few shelters, and lacked the necessary biomass of preferred forbs to sustain the existing population. Additional factors to consider for future reptilian headstart pens include vegetative cover, food sources, soil seed banks, and soil composition.

Journal

Chelonian Conservation and BiologyAllen Press

Published: Jun 16, 2018

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off