Consequences of sensory plasticity in fish

In a recent paper published in Proceedings of the Royal Society of London B (Chapman et al. 2010: http://rspb.royalsocietypublishing.org/content/early/2010/01/05/rspb.2009.2055.full.pdf+html) we report on the consequences of sensory plasticity in a species of freshwater fish, the guppy. Sensory plasticity is a widely documented phenomenon where animals compensate for sensory deprivation in one sense (e.g. vision) by an improvement in the performance of an alternative sense (e.g. smell). Surprisingly the consequences of sensory plasticity for important survival-related behaviours such as locating food have not been tested. In our experiments we show that fish that experience poor visual conditions (low light) in early life make a sensory ‘switch’ to a reliance on ‘smelling’ chemical cues to find food. These fish effectively compensate for difficulty in seeing food by this switch, and we find that fish reared under visually poor conditions will continue to rely on smell even when tested under standard light conditions. Our research suggests that this switch from vision to smell may help individuals to carry out foraging behaviour that is essential to their survival in a visually poor environment. Given that many human activities can affect the sensory environment animals experience (such as increased turbidity in lakes and ponds and acoustic noise in urban environments) the ‘compensatory plasticity’ we find in our study may provide a buffer that allows animals to carry out fundamental behaviours such as finding food in the face of substantial change to the sensory environment.

Thanks to Lesley Morrell for the guppy photo! (http://www.personal.leeds.ac.uk/~bgyljm/)

/Ben

Why do tabanids attack black horses?

In a recent paper published in Proceedings of the Royal Society of London B (Horváth et al. 2010; http://rspb.royalsocietypublishing.org/content/early/2010/01/28/rspb.2009.2202.full.html#ref-list-1) we report on why dark (black and brown) horses suffer from more attacks from blood sucking tabanids (horse flies) compared to white horses. The reason is that the dark coat of the horse reflects polarized light from the sky in a way much similar to a water surface. The blood sucking tabanids are attracted to water to drink and to lay their eggs, and use information from reflected polarized light also to locate hosts. It is the female tabanids that are attracted to the host to suck blood, and use this meal to produce eggs. Tabanid attacks can be severe and cause spreading of diseases to humans and grazing animals as well as reduce milk production in cattle. What we can learn from this is that we shall dress in white cloths and avoid dark, black clothing when in the field, especially when visiting wet areas with high numbers of tabanid flies.
/Susanne

New thesis: flight of swifts

On Friday 29th January 2010, Per Henningsson is defending his thesis on "fluid dynamics, flight performance and flight behavior of common swifts". The defense takes place in the Blue lecture hall at 10:00, with Prof. Bret Tobalske as faculty opponent. On the day before, you can enjoy an extra CAnMove mini-sympoium on the animal flight, starting at 14:00 in the seminar room "Tanken", in which Bret Tobalske will talk on his fascinating research on hummingbird flight. That the swift is a remarkable bird is perhaps not new to most of us, and Per is now getting some well deserved media attention for his spectacular PhD thesis. See e.g.http://www.gp.se/nyheter/sverige/1.296297-flygexpertens-hemlighet-avslojad

Charles Anderson gives lecture about long-distance migration in dragonflies

For those of you who have not already seen this interesting video, take a look! It describes a new long-distance migratory system involving insects - dragonflies! The migration takes place annually, between the two monsoons, from India to Africa and is much more impressive in terms of distance than the more wellknown Monarch butterfly migration in North America. This shows that there is still many new basic things and surprises to discover in nature.

Winter flight of Nyctalus noctula

Today (15 January) three bats have left their hibernation site and are found flying around at midday foraging along the north side of the Ecology Building (Stor fladdermus Nyctalus noctula). One of the bats was chased by a magpie (Pica pica), but escaped capture. You may still see them.

Susanne

Merry Christmas and Happy New Year!

Dear All,

I wish to thank you all for your contributions to CAnMove in 2009. It has been a year full of activities and adventures. New staff and postdocs emplyed, two workshops, the migration course, invited lecturers, a full seminar program, invited speakers and new collaborations. It is with great joy I see how much we have achieved this year, and it is also with great excitement and hope I look forward to the coming year. We will have our first CAnMove conference in Lund, and please note 30 March 2009 for the date. Topic will be technical development and research in our program.

I hope you all take a good rest and enjoy the snow over the Christmas Holiday Season. I look forward to see you again in January 2009!

Best wishes,

Susanne

On satellite telemetry and mortality

In 1996 the first Swedish Ospreys were equipped with satellite transmitters, small electronic devices that allow tracking the movements of individual birds in nearly real-time. For the first time the impressive migratory movements of this raptor bird could be mapped, along with details about stopover behaviour, timing of migration, migration speeds, etc. The satellite tracking program has continued ever since (still running today), in which many individuals of different species of birds have been included. The research has provided many new insights in the migratory behaviours of birds, and resulted in two PhD theses (Nils Kjellén and Roine Strandberg).

Adult female Marsh Harrier “Fe06-66” has just been equipped with a satellite transmitter. The small electronic device allowed us to track the movements of this bird for the rest of its life. This particular female disappeared under suspicious circumstances in France. Most likely she was (illegally) shot by a hunter.

One of the downsides of satellite telemetry is that it is a rather expensive technique, and thus only a small number of birds can be followed every year. Because of these small sample sizes it is extra unfortunate to lose a bird that we are tracking. However, when, where, and under what circumstances migrating animals die is interesting information in itself. It is almost impossible to collect data on this important topic in any other way. Every case of mortality is thus sad but interesting at the same time.

Last locations obtained from the female Marsh Harrier Fe04-53, during her second autumn migration. She started to cross the Mediterranean Sea on the 27th of September under good metrological conditions. Midway the crossing she suddenly stopped moving, and she remained at this location for more than a day. Subsequent signals were received from the south coast of Spain, where the transmitter moved westwards at the speed of a car and disappeared into a small town. The last position was received from a large building. This bird was presumably shot by poachers that await migrating birds in small boats.

After 12 years of tracking migrating raptor birds a sufficiently large dataset on had been accumulated in order to look for patterns in when and where migrants die. In a recent paper we have focussed on risks associated with the crossing of the Sahara Desert, a formidable barrier for billions of Eurasian breeding birds wintering in African. We evaluated about 90 tracks across the desert of Ospreys, Marsh Harriers, Honey Buzzards and Hobbies. The passage turned out to be very hazardous for juvenile birds; during their first autumn migration about one third of the young birds died while attempting crossing the desert. For adult birds only 2% direct mortality was recorded per desert crossing, which still contributes significantly to their annual mortality. Additionally, adult birds showed in nearly half of their crossings aberrant behaviours, like abrupt course changes, slow travel speeds, interruptions and retreats from the desert, indicating problems during the passage. Aberrant behaviours during the crossing in spring resulted in late arrival at breeding grounds and an increased probability of breeding failure (carry-over effects). The Sahara Desert is thus indeed a true barrier for migrating (raptor) birds, and has a major effect on has a major impact on both survival and breeding success.

Juvenile Osprey “Juv61-07” succumbed just before it had completed the crossing of the Sahara Desert. This happens to about one third of the young birds in their attempt to overcome this almost everlasting dry environment.

The death of an Osprey in the desert as seen from GPS location fixes. This particular transmitter was sending for several weeks from exactly the same location. It is impossible for the birds to drop their transmitter, stationary positions thus indicate death.

A collaborator in Mauretania succesfully located a juvenile Osprey that failed to cross the desert. The transmitter was returned to Lund and can thus be used to track another hopefully longer living Osprey.

The paper on risks associated with the crossing of the Sahara Desert can be found at:
http://rsbl.royalsocietypublishing.org/content/early/2009/11/25/rsbl.2009.0785.short?rss=1

(Roine Strandberg, Raymond H.G. Klaassen, Mikael Hake & Thomas Alerstam. 2009. How hazardous is the Sahara Desert crossing for migratory birds? Indications from satellite tracking of raptors. Biology Letters).