Temporary Translocation of Entire Mistletoe Plants to Understand the Mechanistic Basis of Animal Foraging Decisions

Summary

This work outlines a simple experimental procedure to quantify behavioral drivers of foraging decisions in free-living animals, temporarily relocating mistletoe plants to novel locations and measuring visitation rates.

Abstract

Fruiting mistletoes present a model system for understanding decisions made by foraging animals when locating food. Where, when, and how animals find food is central to many ecological questions, relating to the basis of individual foraging decisions and the extent to which these decisions are innate or acquired. Ecologists have paid particular attention to frugivores, quantifying their preference for fruits with specific shapes, colors, or scents, which, over evolutionary time, confer selection for suites of traits in their favored plants whose seeds they disperse.

This work outlines a novel experimental approach to manipulating food plant occurrence and measuring the response of wild, free-living animals, ideally suited to studying the evolutionary origin and ecological maintenance of seed dispersal. This "cut and paste" protocol involves removing an entire fruiting mistletoe plant from its host and either returning it to its original location or moving it to a novel location, affixing it to a 'pseudo-host' of the same or different tree species. By counting visits to the mistletoe and noting the duration, species, and behaviors, a series of comparisons can discern the most important factors affecting foraging decisions and the consequences for both plant and animal. Here, the protocol is illustrated with a case study to determine between-guild differences in mistletoe frugivory.

The experimental approach teases apart the mechanistic basis of search image formation and refinement, spatial learning, interspecific differences in foraging strategies, and how these changes modify seed dispersal effectiveness. Finally, potential modifications are considered with respect to addressing other questions on foraging ecology, plant-animal interactions, and coevolution.

Introduction

How do animals find food? This is a deceptively simple question, integrating cognition, sensory perception, and metabolic demands with habitat structure, interspecific interactions, and variation in resource availability through space and time. Most of the conceptual advances in the understanding of this topic have come from studying captive animals, where resource quality, quantity, and accessibility can be manipulated^1,2. While useful for establishing sensory capabilities, qualitative preferences, and nutritional qualities of food, captive methods do not reveal how animals fulfill these demands in the wild.<....

Protocol

This experimental protocol was developed and experimentally trialled under the provision of and abiding by the Animal Research Authority guidelines of the University of Technology Sydney (UTS ACEC 2013-745). The protocol does not require handling of animals. Native plants were experimentally manipulated under the permission of a National Parks and Wildlife scientific licence (SL101337).

1. Determine suitable site, species, and ethical considerations

1. Choose the ecosystem type and study location.
   1. Look for a suitable site with abundant mistletoes, one regular mistletoe host, and at least one species of ....

Results

Data amounting to a total of 392 h of observation were collected across the 60 replicates, with 26 of the replicate mistletoes receiving visits from 15 species of birds. To determine whether the visiting birds preferred one treatment over another, visitation data were analyzed using generalized linear models (GzLMs)¹⁷ with negative binomial distributions (after^18,19). Four variables were included as covariates: host height, host canopy cov.......

Discussion

This novel method represents a cost-effective means of understanding the mechanistic basis of foraging differences among species and feeding guilds, revealing the critical role of prior learning and spatial awareness in determining how birds find ripe fruit in structurally complex environments. By uncoupling spatial location from other proximate cues, it was possible to demonstrate that generalist frugivores visit plants in known locations, rather than relying on associations with particular habitats, whereas specialists.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Alcohol cleansing pads	Forestry Suppliers	25557	SmartCompliance First Aid Cabinet Refill
Ladder	Forestry Suppliers	90905	Telesteps 12.5’ Telescopic Ladder
Motion-triggered camera	Forestry Suppliers	91269	Reconyx HF2X HyperFire 2 Camera
Nylon cable ties	Forestry Suppliers	17032	Black is the preferred color
Pruning Saw	Forestry Suppliers	81154	Folding model is preferred to minimize injury, with pole mounted saws advisable if ladders cannot be used to accesss high plants