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Food Hoarding and Spatial Memory in Marsh Tits (Poecile palustris) - a Laboratory Study

Urhan, Ali Utku (2013) BIOP32 20121
Degree Projects in Biology
Abstract
Abstract

Storing of food for later consumption is a prevalent behaviour in nature, especially in temperate and boreal regions. Many birds and mammals are food hoarders. While many mammals are larder hoarders most bird species use a strategy called scatter hoarding. Scatter hoarders protect their stored food by spreading it out over a large area in many and separate caches. Many such species are resident and store a large part of their winter sustenance in the autumn. The recovery of dispersed cryptic caches requires an accurate spatial memory of caching locations. Scatter hoarder birds are known for their advanced spatial memory that is superior to that of non-hoarding similar species. The Marsh tit (Poecile palustris) is an 11 gram... (More)
Abstract

Storing of food for later consumption is a prevalent behaviour in nature, especially in temperate and boreal regions. Many birds and mammals are food hoarders. While many mammals are larder hoarders most bird species use a strategy called scatter hoarding. Scatter hoarders protect their stored food by spreading it out over a large area in many and separate caches. Many such species are resident and store a large part of their winter sustenance in the autumn. The recovery of dispersed cryptic caches requires an accurate spatial memory of caching locations. Scatter hoarder birds are known for their advanced spatial memory that is superior to that of non-hoarding similar species. The Marsh tit (Poecile palustris) is an 11 gram passerine in the family Paridae (tits, titmice and chickadees) that is a large-scale hoarder. I have tested wild caught marsh tits' cache retrieval accuracy under laboratory conditions. Marsh tits were allowed to store 5 seeds into 100 different possible caching holes. After five hours and 24 hours retention intervals birds had approximately 40% success. My results were similar to previous studies on marsh tits and their close relatives. Moreover I have discovered that number of searched holes increases when they have no previous memory of caches and they tended to retrieve most of the seeds within first 15 looks. (Less)
Abstract
Popular science summary

Spatial Memory Accuracy in Marsh tits (Poecile palustris) - an experimental study


Food hoarding is a prevalent food protection behaviour in nature and it is performed by variety of animals including some mammals and birds. Two main food hoarding strategies have been observed among animals; larder hoarding and scatter hoarding. Larder hoarders aggregate all their food in one or a few places and they are generally capable of defending their larder. Scatter hoarders, however, spread out caches over a large area and place one or a few food items in each cache. Studies have shown that spatial memory plays an important role for cache retrieval in scatter hoarders. Many of these studies have focussed on a... (More)
Popular science summary

Spatial Memory Accuracy in Marsh tits (Poecile palustris) - an experimental study


Food hoarding is a prevalent food protection behaviour in nature and it is performed by variety of animals including some mammals and birds. Two main food hoarding strategies have been observed among animals; larder hoarding and scatter hoarding. Larder hoarders aggregate all their food in one or a few places and they are generally capable of defending their larder. Scatter hoarders, however, spread out caches over a large area and place one or a few food items in each cache. Studies have shown that spatial memory plays an important role for cache retrieval in scatter hoarders. Many of these studies have focussed on a particular region of the brain, the hippocampus, which is responsible for spatial memory implementation in birds and mammals.

The marsh tit is a deciduous forest bird belonging to the Paridae family which consists of tits, titmice and chickadees. Like other hoarding species in this family, it is a scatter hoarder bird and its hoarding behaviour has been studied extensively. I have tested their spatial memory abilities under laboratory conditions in a design that aimed to evaluate their precise memory accuracy. The experimental setup consisted of ten artificial trees with possible 10 caching location on each tree. Light regime in the laboratory simulated mid-autumn conditions since the hoarding intensity in marsh tits in nature peaks at this time.

The marsh tits were allowed to store 5 seeds into 100 possible caching holes and later allowed to search for their caches after two retention intervals of 5 and 24 hours. Before retrieval, I had removed 2 out of 5 seeds, in order to minimise the risk for satiation effects. Retention intervals I have used were in accordance with birds’ natural foraging behaviour since they frequently retrieve caches within 24 hours. I used their success in the first 5 and 10 retrieval attempts as measures of memory accuracy. I used two different procedures as controls. For the first type of control I allowed the birds to search for caches that I had stored randomly. For the second type of control I allowed the birds to search for caches that had been made by another marsh tit. The rationale was that the birds should have no prior memory for the caches during the control procedures. As an alternative measure of retrieval success I calculated how efficient the birds were at locating seeds by dividing the number of successful attempts by the total number of attempts.

My results were similar to previous studies conducted under laboratory conditions. I showed that marsh tits use memory for cache retrieval and that their memory accuracy is around 40% in the first ten attempts. In the control sessions the number of retrieval attempts were a much higher than in the retrieval sessions probably because the birds have no memory for the location of the caches and thus have to search more randomly to find food. I found an unexpected but interesting difference between the two types of control sessions. The birds did much better when they looked for other individuals' caches than when they searched for the seeds that I randomly cached. This is hard to explain but might depend on a common species specific preference for some types of cache location in marsh tits.

Supervisor: Anders Brodin
Master´s Degree Project 60 credits in Animal Ecology
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Urhan, Ali Utku
supervisor
organization
course
BIOP32 20121
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
4195481
date added to LUP
2013-12-13 14:50:35
date last changed
2013-12-13 14:50:35
@misc{4195481,
  abstract     = {Popular science summary

Spatial Memory Accuracy in Marsh tits (Poecile palustris) - an experimental study


Food hoarding is a prevalent food protection behaviour in nature and it is performed by variety of animals including some mammals and birds. Two main food hoarding strategies have been observed among animals; larder hoarding and scatter hoarding. Larder hoarders aggregate all their food in one or a few places and they are generally capable of defending their larder. Scatter hoarders, however, spread out caches over a large area and place one or a few food items in each cache. Studies have shown that spatial memory plays an important role for cache retrieval in scatter hoarders. Many of these studies have focussed on a particular region of the brain, the hippocampus, which is responsible for spatial memory implementation in birds and mammals.

The marsh tit is a deciduous forest bird belonging to the Paridae family which consists of tits, titmice and chickadees. Like other hoarding species in this family, it is a scatter hoarder bird and its hoarding behaviour has been studied extensively. I have tested their spatial memory abilities under laboratory conditions in a design that aimed to evaluate their precise memory accuracy. The experimental setup consisted of ten artificial trees with possible 10 caching location on each tree. Light regime in the laboratory simulated mid-autumn conditions since the hoarding intensity in marsh tits in nature peaks at this time. 

The marsh tits were allowed to store 5 seeds into 100 possible caching holes and later allowed to search for their caches after two retention intervals of 5 and 24 hours. Before retrieval, I had removed 2 out of 5 seeds, in order to minimise the risk for satiation effects. Retention intervals I have used were in accordance with birds’ natural foraging behaviour since they frequently retrieve caches within 24 hours. I used their success in the first 5 and 10 retrieval attempts as measures of memory accuracy. I used two different procedures as controls. For the first type of control I allowed the birds to search for caches that I had stored randomly. For the second type of control I allowed the birds to search for caches that had been made by another marsh tit. The rationale was that the birds should have no prior memory for the caches during the control procedures. As an alternative measure of retrieval success I calculated how efficient the birds were at locating seeds by dividing the number of successful attempts by the total number of attempts. 

My results were similar to previous studies conducted under laboratory conditions. I showed that marsh tits use memory for cache retrieval and that their memory accuracy is around 40% in the first ten attempts. In the control sessions the number of retrieval attempts were a much higher than in the retrieval sessions probably because the birds have no memory for the location of the caches and thus have to search more randomly to find food. I found an unexpected but interesting difference between the two types of control sessions. The birds did much better when they looked for other individuals' caches than when they searched for the seeds that I randomly cached. This is hard to explain but might depend on a common species specific preference for some types of cache location in marsh tits. 

Supervisor: Anders Brodin
Master´s Degree Project 60 credits in Animal Ecology
Department of Biology, Lund University},
  author       = {Urhan, Ali Utku},
  language     = {eng},
  note         = {Student Paper},
  title        = {Food Hoarding and Spatial Memory in Marsh Tits (Poecile palustris) - a Laboratory Study},
  year         = {2013},
}