Literaturdatenbank
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McCann, M. J. (2011). Burrow characteristics and social elements of captive juvenile bolson tortoises (gopherus flavomarginatus) within a headstart enclosure in new mexico. Unpublished thesis , New Mexico State University, Las Cruces, New Mexico.
Added by: Sarina Wunderlich (30 Jun 2012 22:01:34 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: McCann2011 View all bibliographic details  |
Categories: General Keywords: Schildkröten = turtles + tortoises, Verhalten = ethology Creators: McCann Publisher: New Mexico State University (Las Cruces, New Mexico) |
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| Abstract |
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MANAGEMENT IMPLICATIONS Protective habitat for Bolson tortoises is limited in the wild. The conservation of this species is dependent on captive breeding and repatriation programs to protect young to ensure future population growth. Young tortoises can be raised by headstarting which is a program designed to care for tortoises during their beginning stages. Captive breeding offers close observation and data collected on animals that would be impossible to study in the wild (Nathan, 1979). Although advantageous, data collected may not represent accurate results that would be found in the wild. Captivity with juvenile Bolson tortoises included high densities of animals, excess available burrows, and supplemental food and water. Results were directed towards the management of juvenile Bolson tortoises that may assist in gaining knowledge of wild animals. I found that tortoises occupied all directional orientations of burrows at different times of the active season. Tortoises preferred artificial burrows over building natural burrows which is similar to behaviors of wild young tortoises using pre-existing rodent burrows to conserve energy use. However, there were adequate artificial burrows available and tortoises were not lacking shelter. It is important that the number of available burrows is proportionate to the number of individuals to give tortoises ability to reduce overcrowding and spread of disease. Based on this study, tortoises selected west and north facing burrows and these areas might be preferred during the beginning of the active season (May-June) and east towards the end of the season (July-September). The least occupied orientation was the south facing which is important if space is limiting within a captive enclosure. Locating aggregation of tortoises in the wild would be most effective prior to monsoon season and concentrated in the north facing orientation if elevation and topography were similar to conditions in New Mexico. One observed natural burrow was found shorter than the current modified artificial burrows. Burrow curving may be more important than burrow length because curving allows for thermoregulation and protection from solar radiation which is highest during the active season (Zimmerman et al., 1994). In captivity, artificial burrows can be designed shorter or impressions can be made into the soil for tortoises to modify and create their own natural burrows. At least one artificial burrow should be made for each tortoise if artificial burrows are made in captivity. It is important to provide some artificial burrows or modified natural burrows in captivity because young tortoises often use pre-existing burrows in the wild to reduce energy use. Tortoises selected a wide variety of plants to forage on, however preference was refined to tobosa grass (Pleuraphis mutica) and narrowleaf globemallow (Sphaeralcea angustifolia) during and after monsoon season. Tobosa grass and narrowleaf globemallow plants should be made available to tortoises in captivity. These plants should be abundant in areas where tortoises will be released for both nutritional purposes and shelter location. Tall grasses are used as cover for natural burrows and also allow tortoises to create natural foraging trails that provide shading. Some plant species that are frequently selected and consumed in the wild may be rejected if plants are broken off; (Ashton and Ashton 2008) this was not the case however for Sphaeralcea angustifolia making it an excellent source of food for both captive and wild tortoises (Ashton and Ashton, 2008).
Added by: Sarina Wunderlich |