|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online January 31, 2007
Journal of Experimental Biology 210, 570-577 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02678
Acquiring, retaining and integrating memories of the outbound distance in the Australian desert ant Melophorus bagoti
1 Department of Biological Sciences, Macquarie University, Sydney, NSW 2109,
Australia
2 Centre for the Integrative Study of Animal Behaviour, Macquarie
University, Sydney, NSW 2109, Australia
3 Department of Zoology, University of Zurich, Zurich,
Switzerland
* Author for correspondence at present address: Centre for Visual Sciences, Research School of Biological Sciences, Australian National University, PO Box 475, Biology Place, Canberra, ACT 2601, Australia (e-mail: ajay.narendra{at}gmail.com)
Accepted 4 December 2006
 |
Summary |
|---|
 TOP Summary IntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Key words: ant, distance estimation, acquisition, memory decay, integration, navigation, Melophorus bagoti
|
Introduction |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
). Experienced ants, however, switch to a faster means of
navigation by using visual cues (Harrison
et al., 1989). Pheromone trails are substituted by visual or
self-generated motion cues in solitary foraging ants. Solitary foraging desert
ants usually rely on path integration to home in to their nest. In path
integration, an outward travelling ant keeps track of the distance and
direction travelled from its starting point to compute the shortest return
distance. In featureless landscapes such as salt pans, desert ants of the
genus Cataglyphis use path integration alone to reach the nest, but
also use landmark based route navigation when visual cues are available
(Wehner, 2003). A successful
foraging trip by a desert ant leads to repeated visits to the same foraging
area (Wehner et al., 1983;
Wehner et al., 2004). In
another solitary foraging desert ant, Melophorus bagoti, each
individual ant forages in a particular sector, the distance travelled within
this sector increasing with experience
(Muser et al., 2005). This
results in ants learning the landmarks within their foraging sector. As path
integration is limited in precision
(Müller and Wehner, 1988;
Merkle et al., 2006), when
sufficient route marks are available, ants establish idiosyncratic paths that
meander around familiar tussocks in the desert environment
(Kohler and Wehner, 2005). To
establish such paths ants need to learn and memorize sequences of
landmarks.
Path integration, the primary means of navigation for desert ants over
featureless terrain, has been well studied in Saharan desert ants. These ants
compute the shortest homebound vector, rather than retracing their circuitous
outbound path, to reach the nest (Wehner
and Wehner, 1990). The mechanism involves estimating distances and
determining directions. Celestial cues based largely on polarized light are
known to provide the directional cue to the ants
(Wehner, 1994), while cues
derived from the legs (some form of step counting) provide the ants an
estimate of the distance travelled
(Wittlinger et al., 2006).
Very little is known about the memory properties of distance estimation.
Experiments by Collett et al. revealed that Cataglyphis ants rely
predominantly on their last outbound trip when estimating distance for path
integration (Collett et al.,
2003). Recently, we studied the acquisition, retention, and
integration of odometric memories in C. fortis
(Cheng et al., 2006), an ant
whose primary means of navigation is path integration. In acquisition, the
ants were good at odometry from the start. Six trials of practice did not
improve performance over one trial of training. Odometric memory, however,
showed decay following a 24 h delay, in contrast to the lifelong retention of
memories of landmarks (Wehner,
1981; Ziegler and Wehner,
1997). The ants also did not integrate multiple odometric
memories, basing their odometric estimates solely on the last outbound
trip.
In the present study we ask similar questions of acquisition, retention,
and integration of odometric memories in Melophorus bagoti, a desert
ant whose primary means of navigation is route following. This ant inhabits
the arid ecosystems of Central Australia, which is typically dotted with low
scrubs and trees, forming a landmark-rich habitat. The ant typically
establishes and adheres to familiar routes interwoven around tussocks
(Kohler and Wehner, 2005;
Wehner et al., 2006). However,
when familiar cues are absent and when forced to navigate by estimating
distances, M. bagoti path integrates
(Wehner et al., 2006) and
estimates distances accurately (A. Narendra, manuscript submitted). Despite
the differences in the habitat and navigational strategies, path integration,
when used, serves a similar function in both M. bagoti and C.
fortis. We here compare the functioning of the odometric memories in the
Australian desert ant with that in the Saharan desert ant. We predict: (a)
rapid acquisition with no effect of extended training, (b) decay of distance
memories after a 24 h delay, and (c) no integration over multiple distance
memories, the odometric estimate being based solely on the last outbound
distance travelled.
|
Materials and methods |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
).
The study site was located 10 km south of Alice Springs, Northern Territory,
Australia. The habitat was characteristic of sandy clayey loamy soil with the
ground cover dominated by Buffel grass Cenchrus ciliaris and
overstory by Acacia estrophiolata and Hakea eyreana. M.
bagoti are solitary foraging ants, walk at over 25 cm
s–1, and forage even when surface temperatures exceed
70°C. Most foraging runs are <1 h in duration and <20 m in length
(Muser et al., 2005). M.
bagoti ants feed on elaisomes of Acacia seeds (A. Narendra,
unpublished observations), but are primarily scavengers feeding on insects
roasted in the desert heat, the majority being hymenopterans. They are
polymorphic with a special morph called `repletes' or `honeypots' that acts as
storage vessels to provide the colony with food while they aestivate in the
winter (Conway, 1992).
Experimental set-up
We experimented on one nest at a given time. A rectangular plastic frame
measuring 70 cm by 46 cm was placed with the nest in the centre of the frame
(Fig. 1). The frame had three
slots on one side to which plastic channels were connected. Two of the
channels were outbound channels measuring 6 m and 12 m in length while the
third was an inbound channel whose length was altered to 6 m or 12 m depending
on the experiment in progress. Channels were constructed with 1 m segments (10
cm height and 10 cm width), joined to one another by nuts and bolts. A feeder
was dug into the ground at the end of the outbound channel. Crumbs of cookies
were provided as food for the ants. Sliding gates were used to control the
entry and exit of ants in and out of the channels. A test channel of 32 m
length was placed parallel to the other channels. A measuring tape was placed
along the entire length of the test channel, enabling the observer to read off
the distance travelled by ants.
|
General procedure
Ants reached a feeder by walking in one of the outbound channels. Ants that
were tested immediately without any training were marked after the test (to
ensure they were not tested again). The other ants were marked upon reaching
the feeder for individual identification. After they had picked up a crumb of
cookie, they were released in the inbound channel. The sliding gate on the far
end of the inbound channel was lifted to let the ant into the nest. On its
subsequent trip, the ant was picked up in a plastic vial after it had picked
up a cookie crumb and was either released in the inbound channel for further
training or was taken for a test. Ants were transferred in the dark to a test
channel where they were released 2 m from the far end of the channel
(Fig. 1). The distance
travelled by the ants from the point of release to the point of its first turn
(start of search) provides an ant's estimate of the homebound distance. The
point where the ant turns and walks back by at least 20 cm was identified as
the first turn (Ronacher et al.,
2000; Cheng and Wehner,
2002; Cheng et al.,
2006). First turns were read off from the measuring tape to an
accuracy of 0.1 m.
Acquisition: do ants estimate distances better with practice?
We asked whether ants with more experience would estimate distances better.
We randomly assigned ants to two groups, one trained to 6 m and another to 12
m. Within each of this group, one batch of ants received zero training trial,
another batch received one training trial, while another batch received six
training trials. Zero-trial ants were those ants that reached the feeder for
the first time, following which they were immediately tested. Ants of the
one-trial batch were tested upon their second visit to the feeder, while ants
from the six-trial batch were tested on the ant's seventh visit to the
feeder.
Retention: does the ant's odometric memory decay over time?
The retention experiments were conducted to establish the delay at which
odometric memory decay sets in. Sliding gates of both the 6 m and 12 m
outbound channels were opened and ants were allowed to choose the exit. Ants
that reached the feeder and picked up a cookie were collected in a plastic
vial. One batch of ants were immediately tested to act as a control group,
while others were released after a delay of 24 h, 48 h, 96 h or 192 h. Ants
were individually held captive in natural light conditions in plastic tubes.
Air, moisture, and food were available during captivity. Mortality rate in
captivity averaged across different delay periods was 7%. Ants with different
delay periods were released in the test channel, and their first turns were
recorded. Besides an overall comparison of all delays, we explicitly evaluated
0 h and 24 h delay groups to test the hypothesis that memory decay is found
after a 24 h delay.
Integration: do ants integrate two previously acquired distance memories?
We determined whether ants integrate previous odometric memories with their
last outbound trip, when estimating distance immediately and after a delay of
24 h. We achieved this by training one batch of ants for five trials at 6 m
and another batch for five trials at 12 m. On the sixth outbound trip, ants
trained at 6 m had to travel twice their previously trained outbound distance,
i.e. 12 m, to reach the feeder (6–12 group). On the other hand, ants
trained at 12 m had to travel only half their previously trained outbound
distance, i.e. 6 m, to reach a feeder (12–6 group) on their sixth
outbound trip. Of the ants that arrived at the feeder on their sixth trial,
some were immediately released in the test channel and their first turns were
determined. Some others were captured and kept in natural light conditions and
released in the test channel after a 24 h delay. Their first turns were then
recorded. Since there was no significant difference between zero training
acquisition and zero delay retention groups (6 m:
F1,48=1.76, P=0.19; 12 m:
F1,64=0.01, P=0.90), we pooled the data to
compare them with the immediately tested ants to determine if integration was
occurring.
Analysis
The key dependent variable was the distance of the first turn. Initially
the means and variances at both distances across different conditions were
computed in all the experiments. The means were compared by Welch's ANOVA
using JMP (SAS, 2002), because
the test is suitable for comparing groups with heterogeneity of variance.
Since the data included outliers, we analysed the variance by O'Brien test
using JMP (O'Brien, 1979).
This test is robust against such outliers. We also compared the variance
between groups by using the coefficient of variation (CV) for every group. CV
was computed by dividing the first turns of individual ants by the mean of
their group. This variable was compared in an earlier study on C.
fortis (Cheng et al.,
2006), and we justify its use in the Results section. As a
preliminary analysis, we first looked for a nest effect in all the formal
statistics conducted. None were found, and we will thus ignore the nest factor
in the results, and pool the ants from both the nests.
|
Results |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
), inter-individual s.d. in odometric estimates of M.
bagoti scales with the mean distance estimated, a form of Weber's law. We
thus compared CVs when comparing variances between groups.
Acquisition
We determined if ants improve in estimating distances with training by
comparing ants with zero, one and six training trials that were trained to a
feeder at a particular distance (Fig.
2). At 6 m training distance, distance estimates of ants with
zero, one and six training trials differed significantly (Welch's ANOVA
F2,38.552=9.79, P<0.001), and the unsystematic
scatter (CV) did not (O'Brien's F2,66=2.07,
P=0.135). The mean distance estimates of ants with zero training was
the most accurate among the three training groups. At 12 m training distance,
distance estimates of ants with zero, one and six training trials differed
significantly (Welch's ANOVA F2,49.314=25.91,
P<0.001). Here too, ants with zero training were the most accurate
among the three training groups. At 12 m training distance, the unsystematic
scatter (CV) differed significantly (O'Brien's F2,74=4.98,
P=0.009), with the 1-trial group having the lowest variance in CV. It
should be noted, however, that many ants in the 1-trial group ran close to the
maximum distance. This resulted in a cluster of first turn distances near 30
m, artifactually reducing the variance. Given this artifact with the 1-trial
group, we proceeded to compare the CVs of the 0-trial and 6-trial groups only
to test whether performance improved with practice. The scatter of the two
groups did not differ significantly (O'Brien's F1,49=1.73,
P=0.194).
|
Retention
Ants that arrived at a feeder at 6 m or 12 m distances were released in a
test channel either immediately or after different delay periods. The mean
distance estimates of ants (Fig.
3) gradually decreased as the delay period increased in the 6 m
groups (Welch's ANOVA F4,78=30.06, P<0.001),
whereas there were no significant differences across groups in the
unsystematic scatter (O'Brien's F4,188=1.07,
P=0.37). With increasing delay periods, first turns of ants with 12 m
outbound distance decreased (Welch's ANOVA F4,92=84.74,
P<0.001), while the unsystematic scatter differed significantly
across delay periods (O'Brien's F4,199=2.52,
P=0.04).
|
We also compared the odometric memory decay at 24 h between M.
bagoti ants and C. fortis ants (from
Cheng et al., 2006). To compare
how memory decayed relative to controls (0 h delay), we adjusted the CV of
M. bagoti ants by the ratio of the s.d. values of the two species at
0 h delay. Thus, CVs of M. bagoti at 24 h delay were each multiplied
by the s.d. of CVs of C. fortis ants at 0 h delay and divided by the
s.d. of CVs of M. bagoti ants at 0 h delay. The resulting comparison
of the variances of adjusted CV values showed that they did not differ
significantly between species at 6 m (O'Brien's
F1,63=2.34, P=0.131), but M. bagoti ants
had greater variance at 12 m (O'Brien's F1,60=5.70,
P=0.02). Doing away with the adjustment still resulted in the same
pattern of inferential statistics. Thus, the memory decayed more at 24 h in
M. bagoti ants at 12 m outbound distance. We did not compare species
at longer delays because at those delays, both species started showing a
substantial drop in their odometric estimates.
Integration
To determine if ants integrate memories of distance travelled, we trained
(five trials) two groups of ants to a feeder, one at 6 m and another at 12 m.
On their sixth trip to the feeder, the outbound distance of the 6 m trained
ants was doubled to 12 m and the outbound distance for the 12 m trained ants
was halved to 6 m. Ants that picked up the cookie were tested either
immediately or after a 24 h delay. Ants of the 6 m group
(Fig. 4), which experienced
double the usual outbound distance on their last outbound trip, estimated
their last outbound distance (13.85±6.27 m, mean ± s.d.) when
tested immediately. The 12 m ant groups, which experienced half the usual
outbound distance on their last outbound trip, also estimated their last
outbound distance (6.63±1.62 m, mean ± s.d.) when tested
immediately. After a day's delay, the distance estimates of ants that
experienced doubling (24.73±7.08 m, mean ± s.d.) and halving
(16.65±9.17 m, mean ± s.d.) on their last outbound distance
overestimated their respective outbound distances. Many of the ants from the
12 m group ran the entire length of the channel when released after a 1-day
delay.
|
We then compared the immediately tested ants with those tested after a 24 h delay. A significant difference in mean first turn was found for the 12–6 groups (Welch's ANOVA F1,17=19.31, P<0.001) and for the 6–12 groups (Welch's ANOVA F1,31=23.01, P<0.001). The 0 h delay group had a significantly smaller CV than the 24 h delay group in the 12–6 groups (O'Brien's F1,32=11.29, P=0.002), while in the 6–12 groups, CV did not differ between 0 h delay and 24 h delay groups (O'Brien's F1,33=2.11, P=0.15). It should be noted, however, that many animals in the 24 h delay group ran close to the entire 30 m maximum distance (10 animals ran >26 m before turning); this means that the variance of this group was artifactually reduced.
Comparison of species in control conditions
Finally, we compared our data (Acquisition: 0 training trials, Retention: 0
h delay, and Integration: 0 h delay) from M. bagoti ants with C.
fortis ants (Cheng et al.,
2006). For each group in each species, CV was calculated relative
to the mean of that group. We then compared the CV across species for all
three conditions combined. Other conditions in the Acquisition experiments
were not included because the M. bagoti ants overestimated in those
conditions. At 6 m, the CV did not differ significantly between species in
variance (O'Brien's F1,121=1.62, P=0.205). At 12
m, M. bagoti ants had larger scatter in their CV than C.
fortis ants (O'Brien's F1,138=7.37,
P=0.008). Thus, at longer distances, performance on odometric
estimation in M. bagoti ants is inferior to C. fortis
ants.
|
Discussion |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Path integration functions to estimate the vector (distance and direction from the starting point, typically home) of the current journey. Being a lifeline when other navigation systems fail, path integration must be based solely on the current outbound trip, and not on previous outbound trips. Hence we predicted a lack of increase in accuracy in distance estimation with increase in the number of training trials. At both 6 m and 12 m training distance, ants with no training (0-trial group) were the most accurate in estimating the homebound distance. The average distances estimated by ants with zero training from the 6 m and 12 m group were greater by 0.56 m and 0.93 m than their respective true homebound distances. These mean values do not differ significantly from their respective outbound distances.
An increase in training trials, by either one or six, resulted in ants over estimating their true homebound distance (Fig. 2). At 6 m training distance, the distance estimates of ants with one and six training trials were similar, but both greater than those of ants with no training. At 12 m training distance, 1-trial ants ran much farther than 0-trial ants, running on average a distance nearly twice that of 0-trial ants before turning back, while ants with six training trials estimated a distance 45% greater than ants with zero training. All groups of ants with training overestimated; the 95% confidence interval around the mean exceeded the outbound distance in each group.
A significant difference in the CV values between the training groups was found only at 12 m training distance. This was caused by the 1-trial group, which had a lower variance than the other groups; the 0-trial and 6-trial groups had similar variances. The lower variance in the 1-trial group was an artifact stemming from the fact that this group far overestimated the outbound distance, and many ants ran close to the maximum distance. The length of the test channel thus artifactually reduced the variance in this group. Overall, increase in training did not result in improved performance, confirming predictions.
We interpret the overestimation with training as an effect of learning to
follow a route, an interpretation we also proposed for C. fortis
(Cheng et al., 2006). When the
ants run down the channel on a return journey, they learn to associate the
context of the channel with a route instruction: run along the channel in the
homebound direction until the nest enclosure is encountered. The view of the
end of the channel, with the white walls of the enclosure at the end, might
well form part of the route memory. Route following in both C. fortis
(Wehner et al., 1996) and
M. bagoti (Kohler and Wehner,
2005) is well known. Similar overestimation is found here in the
integration experiment after a delay is imposed before the test (discussed
below). Note that the ants generally did not run all the way down to the end
of the channel. We interpret this to mean that the path integrator continues
to operate in route following, a claim supported by evidence
(Collett et al., 1998;
Andel and Wehner, 2004;
Knaden and Wehner, 2006). When
executing a route, the ants still `listen' to their odometer and turn back to
search when they have travelled too far beyond. Further research would be
required to confirm this interpretation.
Based on our previous study on C. fortis
(Cheng et al., 2006), we
expected an increase in scatter in odometric estimates of M. bagoti
ants after a 24 h delay. Considering that the maximum foraging duration of an
individual ant was 64 min (Muser et al.,
2005), with most foraging trips being much shorter, there is no
requirement for the odometric estimate to last beyond 24 h. As expected, ants
released after a 24 h delay had increased scatter compared with the no-delay
group (Fig. 3). This was the
case even when mean first turn distance was equated between controls and 24 h
delay groups by excluding ants in the 24 h delay groups with the lowest first
turn distances. With other delays, the scatter was similar to the 24 h group;
this no doubt caused the lack of statistically significant results in CV when
all groups at 6 m outbound distance were tested together. The pattern of
odometric memory decay in M. bagoti is similar to the Saharan desert
ant, C. fortis (Ziegler and
Wehner, 1997; Cheng et al.,
2006), which also showed an increase in scatter in their odometric
estimates after a 1-day delay. At 12 m outbound distance, the decay in memory
was greater in M. bagoti ants than in C. fortis ants
(Cheng et al., 2006). This
difference should be treated with caution because in the current study, ants
with a 24 h delay ran a shorter distance on average before turning back. Some
ants might have been engaging in systematic search from the start rather than
estimating the outbound distance (discussed below). This would increase the
variance for reasons other than memory decay. In C. fortis, a 24 h
delay did not lead to significant changes in the average first turn distance
(Cheng et al., 2006).
An increase in the delay to 4 days resulted in the mean first turns of
M. bagoti decreasing. Ants tested after an 8-day delay ran on average
<2 m before turning back. C. fortis behaved similarly after 8 days
of delay (Ziegler and Wehner,
1997; Cheng et al.,
2006). As with C. fortis, we interpret the very short
runs in M. bagoti to indicate that the ants had abandoned path
integration altogether, and turned instead to a search behaviour, usually
exhibited by ants that have run off their entire global vector
(Wehner and Srinivasan,
1981).
In integration experiments, ants based their odometric estimates solely on
the last outbound trip. Ants travelled five times at one outbound distance,
and on the sixth trip, the outbound distance was either doubled or halved.
When immediately tested, the odometric estimates of the integration ants were
similar to those without the previous training at a different outbound
distance (0 h delay group: Retention experiment, 0-trial group: Acquisition
experiment), confirming predictions. Other studies with ants
(Collett et al., 2003) and bees
(Lindauer, 1963) also show
that odometric estimates are predominantly based on the current outbound trip.
The predictions were not confirmed for ants tested after a 24 h delay; these
ants ran much farther than the last outbound distance
(Fig. 4), a pattern also found
in C. fortis (Cheng et al.,
2006). Many ants travelled the entire 30 m distance of the
channel. Similar to acquisition data, we interpret the overestimation to
indicate route-based navigation, including perhaps guidance by a remembered
view of what the end of the channel looked like. This route-based navigation
directs the ants to walk until they encounter the door that leads to their
nest enclosure. Untrained ants did not exhibit this form of a route-based
navigation. We suppose that the switch to route-based navigation occurs in
ants because of a combination of memory decay and multiple training.
The lack of integration in path integration is understandable for
functional reasons. The path integrator functions to compute the last outbound
path and only that, and its output is thus not stored as a long-term memory
(Collett et al., 2003). In
contrast, landmark constellations or the profitability of food patches are
stored in long-term memory (Wehner,
1981; Devenport et al.,
1997; Ziegler and Wehner,
1997), and sometimes integrated. For example, Devenport et al.
provided rats with two `patches' (recessed food magazines separated in space)
from which to retrieve food (Devenport et
al., 1997). Patch A was most profitable in a first phase of
training, while conditions reversed in a second phase and Patch B was most
profitable. When tested immediately after Phase 2 training, rats preferred to
visit Patch B, `betting on' the most recent profitable patch. After a few
hours of delay, however, the rats preferred whichever patch had been most
profitable on average, showing that they remembered and compared all their
past experiences with food in the experimental arena.
What do these findings imply for the ant in its natural habitat? The path
of an ant's route is initially computed by the path integrator. With repeated
experience along a path, cues along the route are used to set up route-based
navigation (Kohler and Wehner,
2005; Wehner et al.,
2006), with path integration as a back-up system. In their usual
foraging grounds M. bagoti exhibits sector fidelity, with the
foraging distance within the sector increasing with an ant's experience
(Muser et al., 2005). This not
only leaves the inexperienced workers to collect food closer to the nest, but
also results in the experienced workers learning the routes, and familiarising
themselves with landmarks they encounter along the route. This is reflected in
the homebound paths of the ants. Rather than taking the direct route, ants
adhere to stereotypical routes and wind around specific tussocks in similar
ways over subsequent trips (Kohler and
Wehner, 2005). Our findings in the channels are consistent with
route learning. Odometric memory is a short-term memory as every outbound trip
is unique for an ant. Ants with multiple experiences to a feeder do not learn
the distance better, but familiarise themselves with the routes. Hence when
trained to different distances they do not integrate distance memories but
switch to a route-based strategy, following a decay in odometric memory.
|
Acknowledgments |
|---|
|
References |
|---|
|
TOPSummaryIntroductionMaterials and methodsResultsDiscussionReferences |
|---|
Andel, D. and Wehner, R. (2004). Path integration in desert ants, Cataglyphis: how to make a homing ant run away from home. Proc. R. Soc. Lond. B Biol. Sci. 271,1485 -1489.[Medline]
Breed, M. D., Fewell, J. H., Moore, A. J. and Williams, K. R. (1987). Graded recruitment in a ponerine ant. Behav. Ecol. Sociobiol. 20,407 -411.[CrossRef]
Cheng, K. and Wehner, R. (2002). Navigating desert ants (Cataglyphis fortis) learn to alter their search patterns on their homebound journey. Physiol. Entomol. 27,285 -290.[CrossRef]
Cheng, K., Narendra, A. and Wehner, R. (2006).
Behavioral ecology of odometric memories in desert ants: acquisition,
retention and integration. Behav. Ecol.
17,227
-235.
Christian, K. A. and Morton, S. R. (1992). Extreme thermophilia in a central Australian ant Melophorus bagoti.Physiol. Zool. 65,885 -905.
Collett, M., Collett, T. S., Bisch, S. and Wehner, R. (1998). Local and global vectors in desert ant navigation. Nature 394,269 -272.[CrossRef]
Collett, M., Collett, T. S., Chameron, S. and Wehner, R.
(2003). Do familiar landmarks reset the global path integration
system of desert ants? J. Exp. Biol.
206,877
-882.
Conway, J. R. (1992). Notes on the excavation of a nest of Melophorus bagoti Lubbock in the Northern Territory, Australia (Hymenoptera:Formicidae). J. Aust. Entomol. Soc. 31,247 -248.
Devenport, L., Hill, T., Wilson, M. and Ogden, E. (1997). Tracking and averaging in variable environments: a transition rule. J. Exp. Psychol. Anim. Behav. Process 23,450 -460.[CrossRef]
Harrison, J. F., Fewell, J. H., Stiller, T. M. and Breed, M. D. (1989). Effects of experience on use of orientation cues in the giant tropical ant. Anim. Behav. 37,869 -871.[CrossRef]
Knaden, M. and Wehner, R. (2006). Ant
navigation: resetting the path integrator. J. Exp.
Biol. 209,26
-31.
Kohler, M. and Wehner, R. (2005). Idiosyncratic route-based memories in desert ants, Melophorus bagoti: how do they interact with path integration vectors? Neurobiol. Learn. Mem. 83,1 -12.[CrossRef][Medline]
Lindauer, M. (1963). Kompassorientierung. Ergeb. Biol. 26,158 -181.
Merkle, T., Knaden, M. and Wehner, R. (2006).
Uncertainty about nest position influences systematic search strategies in
desert ants. J. Exp. Biol.
209,3545
-3549.
Müller, M. and Wehner, R. (1988). Path
integration in desert ants. Proc. Natl. Acad. Sci. USA
85,5287
-5290.
Muser, B., Sommer, S., Wolf, H. and Wehner, R. (2005). Foraging ecology of the Australian desert ant Melophorus bagoti. Aust. J. Zool. 53,301 -311.[CrossRef]
O'Brien, R. G. (1979). A general ANOVA method for robust tests of additive models of variances. J. Am. Stat. Assoc. 74,877 -880.[CrossRef]
Ronacher, B., Gallizzi, K., Wohlgemuth, S. and Wehner, R. (2000). Lateral optic flow does not influence distance estimation in the desert ant Cataglyphis fortis. J. Exp. Biol. 203,1113 -1121.[Abstract]
SAS (2002). JMP Statistics and Graphics Guide, Version 5. Cary, NC: SAS Institute.
Wehner, R. (1981). Spatial vision in arthropods. In Handbook of Sensory Physiology. Vol.VII/6c (ed. H. Autrum), pp.288 -616. Berlin, Heidelberg, New York: Springer.
Wehner, R. (1994). The polarization-vision project: championing organismic biology. In Neural Basis of Behavioural Adaptation (ed. K. Schildberger and N. Elsner), pp.103 -143. Stuttgart, New York: G. Fischer.
Wehner, R. (2003). Desert ant navigation: how miniature brains solve complex tasks. Karl von Frisch Lecture. J. Comp. Physiol. A 189,579 -588.[CrossRef][Medline]
Wehner, R. and Srinivasan, M. V. (1981). Searching behaviour of desert ants, genus Cataglyphis (Formicidae, Hymenoptera). J. Comp. Physiol. A 142,315 -338.[CrossRef]
Wehner, R. and Wehner, S. (1990). Insect navigation: use of maps or Ariadne's thread. Ethol. Ecol. Evol. 2,27 -48.
Wehner, R., Harkness, R. D. and Schimd-Hempel, P. (1983). Foraging strategies in individually searching ants, Cataglyphis bicolor (Hymenoptera, Formicidae). Stuttgart: Fischer.
Wehner, R., Michel, B. and Antonsen, P. (1996). Visual navigation in insects: coupling of egocentric and geocentric information. J. Exp. Biol. 199,129 -140.[Abstract]
Wehner, R., Meier, C. and Zollikofer, C. (2004). The ontogeny of foraging behaviour in desert ants, Cataglyphis fortis. Ecol. Entomol. 29,240 -250.[CrossRef]
Wehner, R., Boyer, M., Loertscher, F., Sommer, S. and Menzi, U. (2006). Ant navigation: one-way routes rather than maps. Curr. Biol. 16,75 -79.[CrossRef][Medline]
Wittlinger, M., Wehner, R. and Wolf, H. (2006).
The ant odometer: stepping on stilts and stumps.
Science 312,1965
-1967.
Ziegler, P. and Wehner, R. (1997). Time-courses of memory decay in vector based and landmark-based systems of navigation in desert ants, Cataglyphis fortis. J. Comp. Physiol. A 181, 13-20.[CrossRef]
This article has been cited by other articles:
|
|
 |
|
  A. Narendra Homing strategies of the Australian desert ant Melophorus bagoti I. Proportional path-integration takes the ant half-way home J. Exp. Biol., May 15, 2007; 210(10): 1798 - 1803. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
