William K. Hayes

Diet and the environment: does what you eat matter?

Food demand influences agricultural production. Modern agricultural practices have resulted in polluted soil, air, and water; eroded soil; dependence on imported oil; and loss of biodiversity. The goal of this research was to compare the environmental effect of a vegetarian and nonvegetarian diet in California in terms of agricultural production inputs, including pesticides and fertilizers, water, and energy used to produce commodities. The working assumption was that a greater number and amount of inputs were associated with a greater environmental effect. The literature supported this notion. To accomplish this goal, dietary preferences were quantified with the Adventist Health Study, and California state agricultural data were collected and applied to state commodity production statistics. These data were used to calculate different dietary consumption patterns and indexes to compare the environmental effect associated with dietary preference. Results show that, for the combined differential production of 11 food items for which consumption differs among vegetarians and nonvegetarians, the nonvegetarian diet required 2.9 times more water, 2.5 times more primary energy, 13 times more fertilizer, and 1.4 times more pesticides than did the vegetarian diet. The greatest contribution to the differences came from the consumption of beef in the diet. We found that a nonvegetarian diet exacts a higher cost on the environment relative to a vegetarian diet. From an environmental perspective, what a person chooses to eat makes a difference.

Effects of a negative pressure venom extraction device (Extractor) on local tissue injury after artificial rattlesnake envenomation in a porcine model

OBJECTIVES To determine if a commercially available negative-pressure venom extraction device (Extractor) reduces local tissue injury after artificial rattlesnake envenomation in a porcine model. METHODS We prospectively studied 10 pigs using a crossover design. After the pigs were anesthetized, 25 mg Crotalus atrox venom was injected obliquely with a 22-gauge needle 7 mm deep into subcutaneous tissues proximal to the ventral hind hoof. Pigs were randomized to receive either the Extractor (applied 3 minutes following envenomation and left in place for 30 minutes) or no Extractor. The protocol was repeated 14 days later by using the alternate treatment group and opposite hind leg for each animal. We measured leg circumference at standardized locations on the hoof, foreleg, and thigh at baseline and then 1, 2, 3, 4, 5, 6, 24, 48, 72, and 96 hours following venom injection. Maximal changes in circumference at 6 hours were compared using the paired t test. Minimum residual swelling at up to 96 hours was similarly compared. RESULTS Maximal 6-hour swelling was similar with and without the Extractor: the hoof difference with the Extractor was -0.1% (95% CI = -3.4% to 3.2%, P = .95), foreleg difference was 0.3% (95% CI = -4.1% to 4.7%, P = .88), and thigh difference was -2.8% (95% CI = -10.0% to 4.4%, P = .40). Minimum residual swelling at up to 96 hours was also similar with and without the Extractor: hoof difference with the Extractor was 1.2% (95% CI = -5.6% to 8.0%, P = .70), foreleg difference was 0.6% (95% CI = -3.7% to 4.9%, P = .76), and thigh difference was 0.3% (95% CI = -2.4% to 3.0%, P = .81). A circular lesion identical in size and shape to the Extractor suction cup, which later necrosed and resulted in tissue loss, developed where the device had been applied in 2 animals. No such lesions occurred in legs not treated with the Extractor. CONCLUSION No benefit was demonstrated from Extractor use for artificial rattlesnake envenomation in our animal study. The skin necrosis noted in 2 Extractor-treated extremities suggests that an injury pattern may be associated with the device.

Northern Pacific Rattlesnakes (Crotalus viridis oreganus) Meter Venom When Feeding on Prey of Different Sizes

taped as they each struck small and large laboratory mice (Mus musculus). Venom measurements were made by enzyme-linked immunosorbent assay (ELISA) of whole-animal homogenate. Although medium and large snakes expended similar quantities of venom, both groups injected significantly more venom into large mice than into small mice. Slow-motion videotape analyses indicated that behavioral aspects of striking were similar for medium and large snakes and did not differ between size classes of prey. Likewise, no behavioral aspect of striking was correlated with the quantity of venom expended. Thus, venom expenditure was not a consequence of or constrained by some extrinsic aspect of striking such as duration of fang contact. Instead, the rattlesnakes metered more venom into larger prey through intrinsic control of venom delivery. Because of the predatory advantages for quick death and efficient digestion of larger prey, injection of more venom into larger prey is likely an adaptive strategy.

Chemical and behavioral ecology of foraging in prairie rattlesnakes (Crotalus viridis viridis)

Free-ranging prairie rattlesnakes (Crotalus viridis viridis) exhibit lengthy vernal migrations upon emergence from winter hibernation. A series of laboratory experiments was designed to test hypotheses regarding the function and causation of vernal movements. Rattlesnakes obtained from Wyoming and Colorado populations were used. First, we hypothesized that the function of vernal movements is to locate small mammal prey. Second, we predicted that activeC. v. viridis use prey chemicals, as well as other cues, to decide whether or not rodents are present in an area. Third, we hypothesized that vernally active males would be more responsive to rodent prey and their odors than females, given observed differences in behavior in the field. Fourth, we predicted that rattlesnakes captured in Colorado would be more sensitive to prey odors than those obtained in Wyoming, because of disparate community structure and, hence, small mammal spatial distributions. As expected, snakes exhibited reduced activity, as well as certain other dependent measures reflecting predatory investigation, in arena zones containing either live rodents or their chemicals. However, responses to the latter were reduced in Wyoming rattlesnakes tested with chemicals from deer mice (Peromyscus maniculatus), relative to Colorado animals tested with chemicals obtained from house mice (Mus musculus). In contrast to patterns observed in nature, males and females exhibited almost no differences in overall responsiveness. Results are discussed in the context of simulation modeling and ongoing studies of prairie rattlesnake behavior.

ONTOGENY OF STRIKING, PREY-HANDLING AND ENVENOMATION BEHAVIOR OF PRAIRIE RATTLESNAKES (CROTALUS V. VIRIDIS)

The ontogeny of striking, prey-handling and envenomation behavior was studied in the prairie rattlesnake (Crotalus v. viridis). Snakes of three size classes (small, medium, large) were allowed to strike and envenomate deer mice (Peromyscus maniculatus) of corresponding size. The mass of venom expended in a single strike, assayed by enzyme-linked immunosorbent assay (ELISA) of whole-mouse homogenates, increased exponentially with length of the snake. Small snakes embedded their fangs in prey for a longer duration than larger snakes. Mice were always struck and released, regardless of snake or prey size. Latency to immobilization was similar for mice envenomated by medium and large snakes; small mice struck by small snakes were not mobile. Latency to death and death rate (latency to death divided by mass of mouse) were greater for mice envenomated by small snakes as compared to medium and large snakes. These findings further clarify the ontogenetic and functional relationships between venom, morphology, diet and behavior. They also illustrate how behavior may be modified to maximize envenomation and feeding success.

Home Range, Spatial Overlap, and Burrow Use of the Desert Tortoise in the West Mojave Desert

Abstract Understanding the space use patterns of a population may provide crucial information regarding land management decisions, such as delineation of protected areas. Herein we provide a comprehensive analysis of factors affecting the space use of Desert Tortoises in the west Mojave Desert, including physical, social, and environmental variables. Our objectives were to determine how spatial overlap, as well as multiple parameters of burrow use, influence home range size of this species. Male tortoises were significantly larger than females and exhibited very different patterns of space and burrow use; however, body size did not affect these variables. Male home range (100% MCP) and core area (50% MCP) size averaged 65% and 73% larger than those of females. Burrow use by males and females affected core area size, but not home range area. Females exhibited a strong male bias in overlap of both estimates of space use and burrow sharing, while using a significantly lower number of burrows per year. However, males overlapped and shared burrows with a similar number of tortoises of either sex. In addition, a high degree of home range overlap between individuals suggests a lack of territoriality in this population, although this warrants further analysis. These results suggest that social factors may not be the primary determinants of space use in this Desert Tortoise population.

Factors associated with the mass of venom expended by prairie rattlesnakes (Crotalus v. viridis) feeding on mice

The purpose of this study was to assess through correlation analyses the various factors and consequences associated with the mass of venom injected by prairie rattlesnakes (Crotalus v. viridis) into their natural prey, deer mice (Peromyscus maniculatus). Fifty-seven predator-prey interactions were studied via slow motion videotape review. The mass of venom expended by snakes during biting was quantified by enzyme-linked immunosorbent assay (ELISA) of whole-animal homogenates. The quantity of venom expended was not related to size of prey; however, the range of mouse sizes (13-31 g) was quite narrow. Multiple bites of the same mouse were not associated with incremental increases in venom expenditure; only about 40% more venom was expended by striking prey a second time. The duration of fang contact and site of fang penetration had no discernible effects on venom expenditure. The site of fang penetration of prey appeared to be random, due to evasive actions of the mice. The components of striking (duration of launch, fang contact, and recoil, respectively) and distance of the strike were correlated and appeared to be influenced by the preys reaction. After striking and releasing mice, the snakes did not attempt to relocate more quickly those prey which succumbed to venom relatively quickly. Both natural (snakebite) and artificial (syringe) injections indicated that the site of venom injection (e.g. anterior, posterior, muscle, vital organ) has a greater influence on subsequent mobility and survival of mice than the quantity of venom injected. It appears that some behavioral aspects of predation (especially the sequential components of striking) are flexible and responsive to prey reactions, while others (venom expenditure and poststrike immobility) are less subject to modification.

Delivery of Duvernoy's secretion into prey by the brown tree snake, Boiga irregularis (Serpentes : Colubridae)

Many colubrid snakes, like the more venomous elapid and viperid snakes, can produce and inject an oral secretion that is toxic and may present a human health risk. However, colubrid oral toxins are produced in a Duvernoys gland and delivered not through a hollow fang, but instead by long, often grooved teeth under low pressure. The possible role of Duvernoys secretion in functions other than rapid killing of prey make it important to know how and where this secretion is delivered during a feeding strike. We used ELISA analysis to determine the quantity and proportional distribution of Duvernoys secretion delivered into the integument compared to the viscera during a feeding strike by the colubrid snake Boiga irregularis. We determined that only about 54% (1-5 mg) of the secretion actually reached the viscera and that the rest remained in the integument. The amount reaching the viscera is about three to eight times the i.p. LD50 for mice, but these snakes depend more on constriction than toxins to kill their prey. Consequently, delivery of Duvernoys secretion by B. irregularis is hypothesized to be part of a digestive function and its toxic properties a byproduct of this role.

Sensationalistic Journalism and Tales of Snakebite: Are Rattlesnakes Rapidly Evolving More Toxic Venom?

Recent reports in the lay press have suggested that bites by rattlesnakes in the last several years have been more severe than those in the past. The explanation, often citing physicians, is that rattlesnakes are evolving more toxic venom, perhaps in response to anthropogenic causes. We suggest that other explanations are more parsimonious, including factors dependent on the snake and factors associated with the bite victims response to envenomation. Although bites could become more severe from an increased proportion of bites from larger or more provoked snakes (ie, more venom injected), the venom itself evolves much too slowly to explain the severe symptoms occasionally seen. Increased snakebite severity could also result from a number of demographic changes in the victim profile, including age and body size, behavior toward the snake (provocation), anatomical site of bite, clothing, and general health including asthma prevalence and sensitivity to foreign antigens. Clinical management of bites also changes perpetually, rendering comparisons of snakebite severity over time tenuous. Clearly, careful study taking into consideration many factors will be essential to document temporal changes in snakebite severity or venom toxicity. Presently, no published evidence for these changes exists. The sensationalistic coverage of these atypical bites and accompanying speculation is highly misleading and can produce many detrimental results, such as inappropriate fear of the outdoors and snakes, and distraction from proven snakebite management needs, including a consistent supply of antivenom, adequate health care, and training. We urge healthcare providers to avoid propagating misinformation about snakes and snakebites.

Poisons, toxungens, and venoms: redefining and classifying toxic biological secretions and the organisms that employ them

Despite extensive study of poisonous and venomous organisms and the toxins they produce, a review of the literature reveals inconsistency and ambiguity in the definitions of ‘poison’ and ‘venom’. These two terms are frequently conflated with one another, and with the more general term, ‘toxin.’ We therefore clarify distinctions among three major classes of toxins (biological, environmental, and anthropogenic or man‐made), evaluate prior definitions of venom which differentiate it from poison, and propose more rigorous definitions for poison and venom based on differences in mechanism of delivery. We also introduce a new term, ‘toxungen’, thereby partitioning toxic biological secretions into three categories: poisons lacking a delivery mechanism, i.e. ingested, inhaled, or absorbed across the body surface; toxungens delivered to the body surface without an accompanying wound; and venoms, delivered to internal tissues via creation of a wound. We further propose a system to classify toxic organisms with respect to delivery mechanism (absent versus present), source (autogenous versus heterogenous), and storage of toxins (aglandular versus glandular). As examples, a frog that acquires toxins from its diet, stores the secretion within cutaneous glands, and transfers the secretion upon contact or ingestion would be heteroglandular–poisonous; an ant that produces its own toxins, stores the secretion in a gland, and sprays it for defence would be autoglandular–toxungenous; and an anemone that produces its own toxins within specialized cells that deliver the secretion via a penetrating wound would be autoaglandular–venomous. Adoption of our scheme should benefit our understanding of both proximate and ultimate causes in the evolution of these toxins.