Using Pharmacological Manipulation and High-precision Radio Telemetry to Study the Spatial Cognition in Free-ranging Animals

Summary

This paper describes a novel protocol that combines the pharmacological manipulation of memory and radio telemetry to document and quantify the role of cognition in navigation.

Abstract

An animal's ability to perceive and learn about its environment plays a key role in many behavioral processes, including navigation, migration, dispersal and foraging. However, the understanding of the role of cognition in the development of navigation strategies and the mechanisms underlying these strategies is limited by the methodological difficulties involved in monitoring, manipulating the cognition of, and tracking wild animals. This study describes a protocol for addressing the role of cognition in navigation that combines pharmacological manipulation of behavior with high-precision radio telemetry. The approach uses scopolamine, a muscarinic acetylcholine receptor antagonist, to manipulate cognitive spatial abilities. Treated animals are then monitored with high frequency and high spatial resolution via remote triangulation. This protocol was applied within a population of Eastern painted turtles (Chrysemys picta) that has inhabited seasonally ephemeral water sources for ~100 years, moving between far-off sources using precise (± 3.5 m), complex (i.e., non-linear with high tortuosity that traverse multiple habitats), and predictable routes learned before 4 years of age. This study showed that the processes used by these turtles are consistent with spatial memory formation and recall. Together, these results are consistent with a role of spatial cognition in complex navigation and highlight the integration of ecological and pharmacological techniques in the study of cognition and navigation.

Introduction

Cognition (herein defined as "all processes involved in acquiring, storing, and using information from the environment" ¹) is central to an array of complex navigation tasks². For example, Sandhill cranes (Grus canadensis) show a marked improvement in migratory precision with experience³, and sea turtle species imprint on their natal beaches as hatchlings and return as adults^4-6. Similarly, successful migration, dispersal, and foraging hinge on an animal's ability to gather information about their spatial environment^7,8. Some animals appear to learn navigational routes in relation to specific ....

Protocol

All procedures involving animal subjects were approved by the Institutional Animal Care and Use Committees of Franklin and Marshall and Washington Colleges and followed all local, state, and federal regulations.

1. Capture and Handling

1. Place hoop traps in the target body of water that is known to contain turtles. Identify water depth ensuring that 4 - 5 inches of the trap remains above water to allow trapped turtles to surface and breathe. Be certain to expand and secure hoop traps to their maximum length with the cross beams to prevent trap collapse. Stake traps into the bed of the body of water to prevent drift.
2. Bait traps with several d....

Results

Using the above protocol, the role of cognition in navigation was assessed in a population of Eastern painted turtles (Chrysemys picta) that has experienced seasonal ephemeral water sources for ~100 years. This population inhabits a mix of ephemeral (drained annually and rapidly - in several hr) and permanent aquatic habitats (Figure 1). Previous studies suggest that after their ponds are drained, resident turtles navigate to alternative water sources with high p.......

Discussion

The protocol presented here allows the experimenter to document and quantify the role of cognition in navigation. Manipulating cognition in the field has proven difficult, as most approaches leave experimenters unable to know which specific aspects of the animal's behavior are being manipulated. However, the protocol presented here allows the experimenter to accurately manipulate and thus assess the role of cognition in navigation. The technique further allows experimenters to monitor animal navigation in real-time w.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Scopolamine bromide	Sigma	S0929	USP
Scopolamine methylbromide	Sigma	S8502, 1421009	USP and non USP versions
Saline	Hanna Pharmaceutical Supply Co., Inc.	409488850	USP, formulated as an injectable
Syringe filter	Fisher	09-720-004
Syringe	Fisher	14-823-30
Hypodermic needle	Fisher	14-823-13
Antenna	Wildlife Materials	3 Element Folding Yagi	Antennae with additional elements are available, but can be cumbersome in the field.
Radio Receiver	Wildlife Materials	TRX-2000S	Water resistant models are also available.
Compass	Brunton	Truarc 15
Radio transmitters	Holohil Inc.	BD-2, PD-2, RI-2B	Transmitter models vary in lifespan and signal output as a function of battery size and pulse rate settings, which can be customized based on the study question and organism.
GPS	Garmin	eTrex Venture
Coaxial cable	newegg.com	C2G 40026	BNC connections are necessary.
Hoop net	Memphis Net and Twine	TN325	Net mesh size should be chosen based on the minimum size of the target animal.