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Mark Robert Sandfoss

Publications and source records attributed to Mark Robert Sandfoss.

12 recordsLinked to original sources
USGS2026

Characterizing the annual cycle of steroid hormones in males from an invasive vertebrate (Python bivittatus) of management concern

South Florida's subtropical climate has facilitated the establishment of numerous invasive species, including the Burmese python ( Python bivittatus ). Despite decades of efforts to manage the invasive python population across South Florida, we lack a comprehensive understanding of their reproductive physiology, limiting the development of targeted control strategies. Here, we characterized seasonal patterns of testosterone (T) and corticosterone (CORT) in free-ranging adult male pythons and evaluated environmental correlates of hormone variation. Results indicate that T peaks before the onset of the breeding season and declines through the season to baseline levels in the non-breeding season. CORT did not show a clear seasonal trend but showed greater variability during the breeding season. These findings reveal that photoperiod and ambient temperature are key environmental correlates of male hormone cycles, contributing to our understanding of the endocrine phenology of a tropical ectotherm in a novel environment.

Florida↗
USGS2026

Case report: Observations on expulsions from 20 years of radiotransmitter implantation in adult Burmese pythons

Background Radiotelemetry as a research tool has advanced our understanding of snake behavior and ecology. However, surgical transmitter implantation can lead to health complications for study animals, including expulsion, which may also interfere with research objectives. Two implantation methods include intramuscular and coelomic placements, and we evaluate expulsion rates of transmitters using these methods in Burmese pythons ( Python bivittatus ) in southern Florida. Results From 2005 to 2024, we implanted 305 transmitters in 142 adult Burmese pythons, primarily using intramuscular implantation ( n = 221), then transitioning to include coelomic placement ( n = 84). There were no observations of transmitter-related mortality. Overall, 98.7% of transmitters were retained, with a 1.3% expulsion rate ( n = 4 transmitters). Expelled transmitters were only observed in intramuscularly implanted transmitters from 4 of 13 gravid females. Conclusions We observed no mortality related to transmitter implantation and few instances of transmitter expulsion, indicating that both intramuscular and coelomic implantation techniques are effective for monitoring adult pythons in the wild. However, there is some risk that females may expel transmitters when gravid, and this risk may be reduced when implanting transmitters intracoelomically. Our findings may be useful for studies of other large-bodied snake populations worldwide where radiotransmitter implantation is appropriate and logistically feasible.

Florida↗
USGS2026

Efficacy of increased visual and olfactory cues for luring and trapping invasive tegu lizards

Controlling invasive wildlife species relies on the ability to efficiently remove individuals from the invaded environment. Thus, maximizing capture potential is of high interest, particularly for species that are difficult to capture. For invasive species such as the Argentine black and white tegu lizard ( Salvator merianae ), increasing attraction to traps could increase the probability of removal. While it has been established that S. merianae can be lured with a single chicken egg, the efficacy of increasing olfactory or visual cues to increase tegu captures has not been rigorously tested. To test this, we leveraged an ongoing National Park Service trapping effort near Everglades National Park. In 2023 and 2024, we randomly assigned traps to a control treatment (single real egg), increased olfactory and visual treatment (three real eggs), an increased visual plus standard olfactory treatment (one real egg and one decoy egg, or one real egg and two decoy eggs), or visual treatment only (three decoy eggs). We fitted Bayesian binomial models for tegu lizards and non-target species to the trapping data to assess how bait treatment, trap style, and trap location affected the daily probability of capture at a trap. Additionally, we fitted Bayesian linear models to test the effect of bait treatment on the size of tegus captured. We found that increasing the olfactory cue to three real eggs increased the probability of tegu capture, but not the probability of non-target species capture. Conversely, traps with one real egg and two decoy eggs increased the probability of non-target captures while reducing the probability of tegu captures. Trap style and trap location also had statistically significant effects. Bait treatment did not significantly influence the size of tegus captured; however, there was a weak effect suggesting juvenile and male tegus captured in traps with three real eggs were larger compared to traps with a single egg and two decoy eggs. Our results highlight potential improvements in tegu control methods that balance effective capture with minimizing non-target bycatch.

Florida↗
USGS2025

Cold-induced vomiting of a white-tailed deer (Odocoileus virginianus) by an invasive Burmese python (Python bivitattus) in Big Cypress National Preserve, Florida, USA

The Burmese python ( Python bivittatus ) is native to Southeast Asia and has an established invasive population throughout South Florida. As part of the effort to understand invasive python biology and potential impacts to the native ecosystem, we have been using radio-telemetry to investigate feeding rates of adult female pythons. The body size and gape of adult Burmese pythons enable them to consume large native prey items including, but not limited to, white-tailed deer ( Odocoileus virginianus ). As an ectothermic species, Burmese pythons' physiological processes, including digestion, are temperature dependent, which may limit their potential invasive range. The low temperature threshold for python digestion is thought to be 20°C within a laboratory setting. Here, we detail an observation of a radio-telemetered female Burmese python that ingested an adult white-tailed deer, retained the deer within the digestive tract for 10 days, and then vomited the deer coinciding with a drop in air temperature as low as 9.4°C. The python survived the vomiting and was alive at the time of publication. To our knowledge, this is the first observation of a free-ranging Burmese python vomiting a deer within the invasive range without direct disturbance from humans at the time of vomiting. This observation provides additional evidence regarding the limits of thermal tolerance, digestion, and feeding habits of invasive Burmese pythons.

Florida↗
USGS2025

An early detection rapid response case study of the Black and White Tegu (Salvator merianae) and implications for a broader framework

Documentation of successful early detection rapid response (EDRR) efforts is lacking from the scientific literature but is needed to inform invasive species response protocols. The Black and White tegu (Salvator merianae) has become established in several Florida counties and its spread is of significant conservation concern. It is of high priority for state and federal managers to prevent the spread into sensitive ecosystems, including the Greater Everglades. Thus, coordinated EDRR efforts are essential given limited infrastructure and funding for such tasks. While tegus have been observed along the eastern boundary of Everglades National Park, there has been no evidence tegus are established within Big Cypress National Preserve. On 8 August 2024 an individual tegu was sighted by a U.S. Geological Survey (USGS) biologist in Big Cypress National Preserve who alerted National Park Service (NPS) staff and mobilized a response. Live traps were placed at the location of sighting within 24 hours and an individual tegu was captured on 13 August 2024. The individual tegu was determined to be the same individual that was observed five days early based on color, pattern, and other physical characteristics. No additional tegus were captured. The rapid, coordinated response of NPS and USGS likely contributed to this successful EDRR event, and highlights the need for more expansive EDRR frameworks at multiple jurisdictional scales.

Florida↗
USGS2024

Flooding-induced failure of an invasive Burmese Python nest in southern Florida

It is important to understand the factors affecting the reproductive success of an invasive species to estimate population size and develop management plans. There remains much we do not understand about the reproductive biology of invasive Burmese Pythons in both their native and invasive range. Oviposition site selection is an important factor in determining reproductive success as nesting is a vulnerable period in the life of reptiles. Flooding can be particularly influential for nesting outcomes and success of developing embryos in habitats that experience periods of heavy rainfall or seasonal flooding. It is not clear how seasonal flooding may impact oviposition site selection by females or hatchling survival of Burmese Pythons in Florida. On 10 May 2023, a radio-transmitted female python oviposited in a hollow log and during incubation all eggs were completely submerged for variable amounts of time. All eggs were collected (n = 78) and dissected to confirm fertilization and assess the stage of embryo development. Two eggs were found to be infertile, while the remaining fertile eggs contained embryos that died at various stages of development. The observed failure of this python nest was a direct result of oviposition site selection by the female. The frequency at which females lay eggs in suboptimal locations in southern Florida is currently unknown. This maladaptive behavior would suggest Burmese Pythons have fitness levels below theoretical optima.

Florida↗
USGS2023

Burmese python size and reproduction: Fact vs fiction

We’ve probably all heard rumors about monster 25-foot snakes or baby pythons emerging from under neighbors houses year-round, but what is fact vs fiction? To help us sort truth from myth, invasive pythons that were removed from the Everglades and surrendered to the National Park Service (NPS) were scientifically investigated via a partnership with the U.S. Geological Survey Fort Collins Science Center’s (USGS FORT) Invasive Species Science Branch. Other contributing partners were South Florida Water Management District and Florida Fish and Wildlife Conservation Commission’s Python Contractor and Agent programs. Over the past 25 years more than 4,000 wild Burmese pythons have been found and removed from southern Florida’s Greater Everglades Ecosystem.

Everglades Cooperative Invasive Species Management↗