Source: CORNELL UNIVERSITY submitted to
INTEGRATING PEST CONTROL AND RESOURCE CONSERVATION: THE POTENTIAL BENEFITS OF RODENT-FEEDING SNAKES TO AGRICULTURISTS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
0194145
Grant No.
(N/A)
Cumulative Award Amt.
(N/A)
Proposal No.
(N/A)
Multistate No.
(N/A)
Project Start Date
Oct 1, 2002
Project End Date
Sep 30, 2005
Grant Year
(N/A)
Program Code
[(N/A)]- (N/A)
Project Director
Adler, K.
Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853
Performing Department
NEUROBIOLOGY AND BEHAVIOR
Non Technical Summary
Snakes are often extirpated from agricultural areas despite the fact that they are prolific rodent feeders. This human-wildlife conflict might be reduced if more convincing evidence existed for the benefits provided by rodent-eating snakes. The purpose of this research is to evaluate the potential for rattlesnakes and their relatives to serve as natural controls of rodent pest populations.
Animal Health Component
25%
Research Effort Categories
Basic
75%
Applied
25%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1350830106012%
1350830107013%
1350840106012%
1350840107013%
1353999106012%
1353999107013%
1357299106012%
1357299107013%
Knowledge Area
135 - Aquatic and Terrestrial Wildlife;

Subject Of Investigation
0840 - Fur-bearing animals; 3999 - Animal research, general; 0830 - Wild animals; 7299 - Research equipment and methods, general/other;

Field Of Science
1060 - Biology (whole systems); 1070 - Ecology;
Goals / Objectives
Over 20 species of rodent-feeding venomous snakes are distributed throughout the United States, from coast to coast. In many areas, including parts of NY, these snakes are common, but rarely encountered due to their secretive nature. All of these snakes are in the family Crotalidae, and all use the same basic foraging strategy for finding and consuming their rodent prey: they strike from ambush, having used chemical cues to locate a suitable ambush site. Most of these species are specialized rodent feeders, and so might provide a substantial benefit to agriculturists in terms of controlling rodent pests such as voles, mice, and rats, which cause billions of dollars in agricultural damage annually. However, the ability of snakes to act as biological controls of rodent pests rests on several untested assumptions about their foraging behavior. It is important to fully realize the benefits of snakes to agriculturists, since venomous snakes have historically been eradicated from agricultural areas. It is also important that behavioral interactions between snakes and rodent pests be examined because many rodent pests are non-native, and snakes may not respond as strongly to non-native prey species as to native ones. No previous studies have been conducted on the development of prey recognition in crotalid snakes, and only a few indirect estimates of the prey consumption rate have been made for crotalids, none of which involve major pest species. Finally, in addition to consuming rodents, the mere presence, or perhaps even odors, of crotalid snakes in agricultural areas may serve as a rodent deterrent. Some rodents actively avoid habitats containing chemical cues from other rodent-feeding snakes, and it is important to examine these interactions between crotalid snakes and rodent species that are agricultural pests. The objective of this project is to study behavioral interactions between timber rattlesnakes and rodents in order to evaluate the effects crotalid snakes may have on pest rodent populations. Specifically, this project will examine: (1) The ability of crotalid snakes to recognize novel rodent species by chemosensory cues and incorporate them into their diet; (2) How the use of chemical cues by both rodents and snakes may affect rodent abundance and activity in agricultural areas.
Project Methods
In order to achieve the listed objectives, three groups of experiments will be performed, which address the following questions: (1) Do crotalid snakes recognize chemical cues from non-native prey in a foraging context? The ability of crotalid snakes to recognize chemical cues from novel rodent species will be assessed by laboratory trials with captive-raised timber rattlesnakes. The general procedure used is as follows. Snakes are introduced to a testing arena containing chemical trails made from different potential prey species. To provide these chemical cues, an aqueous extract is made from the skin surface of a sample prey. The behavior of the snake toward the chemical cues is video recorded, and several stereotyped foraging behaviors are then measured to determine whether or not timber rattlesnakes respond positively to chemical trails from particular species. (2) At what rate do crotalid snakes successfully capture and consume rodents? For this study, free-ranging timber rattlesnakes from populations will be implanted with radio transmitters so that focal individuals can be easily relocated for observation and data collection. Ten individuals from a given denning area will be captured upon emergence and surgically implanted with radio transmitters. These individuals will then be released and relocated for observation. To quantify the rate at which prey are captured and consumed, individuals exhibiting characteristic foraging behaviors will be observed with a motion-sensitive video camera. Since snakes will wait for several hours, or even days, at a given site, it is not feasible to observe their feeding behavior directly. Instead, a low-light video camera will be attached to a motion-sensitive video camera controller. The motion sensor is sensitive to movement by endothermic animals, and will thus automatically record any potential or actual encounters between foraging snakes and rodent prey. (3) Do chemical cues from crotalid snakes affect the behavior of rodent pest species? Several laboratory trials will be conducted as a preliminary test of the hypothesis that odors derived from crotalid snakes deter wild-caught rodent pest species. For these trials, rodent subjects will be taken from the captive colony and transported to a trial Y-maze apparatus containing an aqueous extract from the skin surface of a snake at one end of the Y-maze. The rodent will be released in the unoccupied arm, and its behavior in the maze will be videotaped. From the tapes, several behavioral parameters will be measured indicating the overall response of the rodent toward the snake chemical cues. Trials will be conducted with both crotalid snake chemical cues, and chemical cues from garter snakes (Thamnophis sirtalis), which do not feed on mammals. Trials conducted with crotalid snake odors will be compared to garter snake trials to determine the effectiveness of crotalid odors in repelling rodents.

Progress 10/01/02 to 09/30/05

Outputs
Collectively, snakes feed extensively on rodent pests that cause billions of dollars in agricultural damage annually, such as voles, mice, and rats. The objective of this project was to study behavioral interactions between timber rattlesnakes and rodents in order to evaluate the effects snakes may have on pest rodent populations. Specifically, we examined: (1) the ability of snakes to recognize novel rodent species by chemosensory cues and incorporate them into their diet; and (2) the degree to which snake predation may impact rodent population. To date, we have completed a comprehensive analysis of the foraging ecology of timber rattlesnakes, examining food habits throughout the range of the species. This was done by examining stomach contents of timber rattlesnakes present in the collections of various museums. We have also collected extensive information on how ambush foragers respond to different types of information derived from their prey. This was done by examining the ability of timber rattlesnakes to respond to odor cues from different prey species. Additionally, we have conducted field investigations collecting a large amount of data on natural interactions between rodents and timber rattlesnakes. This was done by following the movements of radio-tagged snakes in the field, and using fixed videography to monitor their encounters and interactions with potential prey species while foraging. Together, these results provide a comprehensive view of how these predators affect prey populations, and the ability of snakes to incorporate novel rodent pest species into their diet.

Impacts
This project examined interactions between rodents and snakes in several different contexts, thus providing baseline data needed to determine the potential of snakes to act as a natural control of rodent pests. Because they are rodent predators, wildlife conservationists often cite the value of snakes as biocontrol agents, providing a commercial impetus for their preservation. However, the ecology of most snake species is poorly understood, and very few relevant data have been collected that would speak to their ability to affect rodent populations. Thus, this project is important because it provides a solid foundation to evaluate a common claim, and may increase leverage for the conservation of important wildlife species by analyzing some of their potential economic value.

Publications

  • Clark, R.W. 2005. Pursuit-deterrent communication between prey animals and timber rattlesnakes (Crotalus horridus): the response of snakes to harassment displays. Behavioral Ecology and Sociobiology 20:1-4.


Progress 01/01/04 to 12/31/04

Outputs
Collectively, snakes feed extensively on rodent pests that cause billions of dollars in agricultural damage annually, such as voles, mice, and rats. The objective of this project is to study behavioral interactions between timber rattlesnakes and rodents in order to evaluate the effects snakes may have on pest rodent populations. Specifically, we examined: (1) The ability of snakes to recognize novel rodent species by chemosensory cues and incorporate them into their diet; (2) The degree to which snake predation may impact rodent population. To date, we have completed a comprehensive analysis of the foraging ecology of timber rattlesnakes, examining food habits throughout the range of the species. This was done by examining stomach contents of timber rattlesnakes present in the collections of various museums. We have also collected a great deal of information on how ambush foragers respond to different types of information derived from their prey. This was done by examining the ability of timber rattlesnakes to respond to odor cues from different prey species. Additionally, we have conducted field investigations collecting a large amount of data on natural interactions between rodents and timber rattlesnakes. This was done by following the movements of radio-tagged snakes in the field, and using fixed videography to monitor their encounters and interactions with potential prey species while foraging. Together, these results are being used to provide a comprehensive view of how these predators affect prey populations, and the ability of snakes to incorporate novel rodent pest species into their diet.

Impacts
This project examines interactions between rodents and snakes in several different contexts, thus providing baseline data needed to determine the potential of snakes to act as a natural control of rodent pests. Because they are rodent predators, wildlife conservationists often cite the value of snakes as biocontrol agents, providing a commercial impetus for their preservation. However, the ecology of most snake species is poorly understood, and very little relevant data has been collected that would speak to their ability to affect rodent populations. Thus, this project is important because it will provide a solid foundation to evaluate a common claim, and may increase leverage for the conservation of important wildlife species by analyzing some of their potential economic value.

Publications

  • Clark, R. W. 2004. Feeding experience modifies the assessment of ambush sites by the timber rattlesnake, a sit-and-wait predator. Ethology 110: 471-483.
  • Clark, R. W. 2004. Timber rattlesnakes (Crotalus horridus) use chemical cues to select ambush sites. Journal of Chemical Ecology 30(3): 607-617.


Progress 01/01/03 to 12/31/03

Outputs
To date, we have completed a comprehensive analysis of the foraging ecology of timber rattlesnakes, examining food habits throughout the range of the species. We have also conducted an examination of how these animals derive information about their rodent prey, both in the laboratory and the wild. Additionally, we have conducted field investigations collecting a large amount of data on natural interactions between rodents and timber rattlesnakes. These results are currently being analyzed and published. It is expected that this analysis will be completed within the next six months.

Impacts
This project will examine the impact of venomous snakes on rodent populations, thus determining their potential to act as a natural control of rodent pests. The potential value of such species as biocontrol agents is often cited as a reason for their conservation, but very little relevant data has been collected prior to this project. Thus, this project will increase leverage for the conservation of important wildlife species by analyzing some of their potential economic value.

Publications

  • Clark, R.W. 2002. Diet of the timber rattlesnake, Crotalus horridus. Journal of Herpetology 36:494-499.