Odors as navigational cues for pigeons
Volatile organic compounds identified that can be used for olfactory navigation by homing pigeons

Date:
October 19, 2020
Source:
Max-Planck-Gesellschaft
Summary:
Volatile organic compounds identified that can be used for olfactory
navigation by homing pigeons.



FULL STORY ========================================================================== Odors are known to be essential for navigation during homeward orientation
and migration of some bird species. Yet little was known about their
chemical composition. An international team has now identified volatile
organic compounds that can be used for olfactory navigation by homing
pigeons and proved the existence of suitable regional chemical gradients
in the air on a landscape-scale in Tuscany.


==========================================================================
Many bird species can find their way home even after being brought to
remote or unfamiliar locations. Over 40 years of research on homing
pigeons have shown that environmental odors play a crucial role in
this process. Yet the chemical identity of these odors has remained
a mystery. An international team of scientists from the Max Planck
Institutes for Chemistry (Mainz) and of Animal Behavior (Radolfzell),
and the Universities of Konstanz, Pisa and Mainz has now identified
potential chemical navigational cues that could be used by homing
pigeons. Based on the collected data, the researchers were also able to
create regional olfactory maps for marine emissions, biogenic compounds,
and anthropogenic mixed air and to establish the existence of regional navigable chemical gradients in the air.

During the scientific mission, which took place in 2017 and 2018 in the
Italian region of Tuscany, the researchers measured a suite of airborne volatile organic compounds (VOCs) over a period of months at the pigeon's
home aviary.

Some of these compounds are emitted by trees, the pine fragrance one
smells during a walk in the forest. Other pungent natural emissions come
from the sea, while still further VOCs can be emitted from industry. The measurements enabled regional maps to be constructed connecting chemicals
with wind direction and speed. Additional measurements were taken in
selected regional forest environments and by air using an ultralight
plane flying at 180 meters -- the average altitude of flying pigeon. The scientists merged the information they had gathered during the field
campaigns with GPS tracks obtained from released birds. Thus, they
generated multiple regional, horizontal and vertical spatial chemical
gradients that can form the basis of an olfactory map.

Olfactory maps based on environmental odors "Ornithologists from Germany
and Italy have shown in more than 40 years of experiments, that pigeons
use airborne odors to navigate home," explains Nora Zannoni, post-doctoral researcher at Max Planck Institute for Chemistry and the study's first
author. Those results have shown that pigeons construct an olfactory
map based on the distribution of environmental odors they have perceived
over several months at the home aviary. This knowledge is then used as a compass at the point of release to return back home from unfamiliar sites.

"By proving the existence of regional chemical gradients in the air
around the experimental site we provide support for the olfactory
navigation hypothesis and with atmospheric measurements we have found
which chemicals can be used for navigation," adds Zannoni. Some compounds
come from forested areas (monoterpenes) or the sea (DMS) while others
are emitted from cities and industrial complexes (trimethylbenzene),
spots that act like chemical lighthouses.

One of the biggest challenges during this research campaign was its multidisciplinary character. "We had to combine the different approaches
of several scientific disciplines -- atmospheric and analytical chemistry, ornithology and animal behavior, computer science and statistics,"
says Martin Wikelski, managing director at the Max Planck Institute of
Animal Behavior.

"It's amazing really," adds Jonathan Williams the project leader at the
MPIC's Atmospheric Chemistry Department in Mainz. "We uncovered these
chemical gradients using several tones of ultrasensitive scientific
equipment, but the same complex odor information can be analyzed and
converted to a regional map by a 400-gram pigeon."

========================================================================== Story Source: Materials provided by Max-Planck-Gesellschaft. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Nora Zannoni, Martin Wikelski, Anna Gagliardo, Atif Raza, Stefan
Kramer,
Chiara Seghetti, Nijing Wang, Achim Edtbauer, Jonathan Williams.

Identifying volatile organic compounds used for olfactory
navigation by homing pigeons. Scientific Reports, 2020; 10 (1)
DOI: 10.1038/s41598-020- 72525-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201019090111.htm

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