Richard E. Mauldin

Environmental temperatures, physiology and behavior limit the range expansion of invasive Burmese pythons in southeastern USA

A well-established population of Burmese pythons resides in the Everglades of southern Florida. Prompted in part by a report that identified much of southern USA as suitable habitat for expansion or establishment of the Burmese python, we examined the plausibility of this snake to survive winters at sites north of the Everglades. We integrated daily low and high temperatures recorded from October to February from 2005-2011 at Homestead, Orlando and Gainesville, Florida; and Aiken, South Carolina, with minimum temperatures projected for python digestion (16 °C), activity (5 °C) and survival (0 °C). Mean low and high temperatures decreased northward from Homestead to Aiken and the number of days of freezing temperatures increased northward. Digestion was impaired or inhibited for 2 months in the Everglades and up to at least 5 months in Aiken, and activity was increasingly limited northward during these months. Reports of overwinter survivorship document that a single bout of low and freezing temperatures results in python death. The capacity for Burmese pythons to successfully overwinter in more temperate regions of the USA is seemingly prohibited because they lack the behaviors to seek refuge from, and the physiology to tolerate, cold temperatures. As tropical Southeast Asia is the source of the Everglades Burmese pythons, we predict it is unlikely that they will be able to successfully expand to or colonize more temperate areas of Florida and adjoining states due to their lack of behavioral and physiological traits to seek refuge from cold temperatures.

Tools for managing invasions: acceptance of non-toxic baits by juvenile Nile monitor lizards and Burmese pythons under laboratory conditions

Nile monitor lizards (Varanus niloticus) and Burmese pythons (Python molurus bivittatus) are large, invasive, predatory reptiles, which are now well established in south Florida. Acetaminophen was recently shown to be lethal to both animals and therefore has potential for inclusion in an integrated pest management effort to control these species. However, acceptable bait matrices for both species are still needed to deliver the toxicant. We tested nine candidate bait matrices on juvenile Nile monitor lizards and Burmese pythons in the laboratory. Baits were tested fresh and also after aging at 30°C and 50% relative humidity for 24 h. Six of the nine baits were well accepted by the monitors in both fresh and aged conditions (dead neonatal mouse, dead quail chick, ground turkey, chicken liver, tilapia, and zebra finch egg). Only the fresh dead neonatal mouse and fresh dead quail chick were well accepted by the pythons. As far as we are aware, these tests are the second of such bait matrix preference tests conducted for reptiles. The implications of our results are discussed regarding further development and testing of baits in a natural setting.

DiazaCon reduces black-tailed prairie dog reproduction in Colorado

Abstract Context. Black-tailed prairie dogs (Cynomus ludovicianus) often come into conflict with humans in urban natural areas adjacent to private property by destroying plants and denuding the landscape. There is a diversity of attitudes related to urban prairie dog management in Colorado and interest in non-lethal methods is increasing. Therefore, the development of non-lethal methods that allow the existence of prairie dogs and mitigate damage related to population density is needed. Aims. The efficacy of DiazaCon (20,25-diazacholesterol dihydrochloride, a cholesterol analogue) as an oral contraceptive bait for reducing reproduction in black-tailed prairie dogs was tested. Persistence of DiazaCon in black-tailed prairie dogs 11 months after initial application was also determined. Methods. Prairie dogs were baited with DiazaCon-coated rolled oats or control bait for 10 days over a 20-day period in November 2007 on one control and one treatment site. Sites were randomly assigned to a treatment group. Visual counts were used 8 months post-treatment (June/July 2008) to determine pup : adult ratios on both sites. Prairie dogs on both sites were trapped 11 months post-treatment (September/October 2008) to gather mass and age data to assess juvenile : adult ratios and to collect blood samples for determination of serum cholesterol and desmosterol concentrations. Key results. DiazaCon treatment reduced the number of pups per adult by 95.5% when compared with the control site in June/July 2008 (0.09 ± 0.02, n = 10, number of observation days) versus 2.0 ± 0.2 (n = 10). Free serum cholesterol levels in treated animals (370.7 µg mL–1) were lower than control animal levels (411.6 µg mL–1, P < 0.015), while treated desmosterol levels (14.5 µg mL–1) were higher than controls (0.35 µg mL–1, P < 0.02) 11 months after ingestion of DiazaCon bait. However, these differences would likely not have been sufficient to prevent successful breeding in the upcoming breeding season. Conclusions. DiazaCon is an effective contraceptive in black-tailed prairie dogs. It is probably reversible and will likely affect breeding success for only one breeding season. DiazaCon may provide an additional tool to help manage urban populations of prairie dogs in locations where lethal control is unacceptable. Implications. The need for further research into secondary hazards to non-target animals, such as predators, is discussed. Recommendations for field application are also discussed.