Orientation and homing success of experienced and inexperienced anosmic pigeons

Savini

et al. 2006

SUMMARY The ability of pigeons to find their way home from unfamiliar sites located up to hundreds of kilometers away is well known, but the mechanisms underlying this ability remain controversial. One proposed mechanism is based on the suggestion that pigeons are equipped with magnetoreceptors that can enable the detection of either the earth's magnetic field and/or magnetic field anomalies in the local terrain over which the pigeons fly. Recent reports have suggested that these magnetoreceptors are located in the upper beak where they are innervated by the ophthalmic branch of the trigeminal nerve. Moreover, this nerve has been shown to mediate pigeons' ability to discriminate the presence versus the absence of a magnetic field anomaly in a conditioning situation. In the present study, however, we show that an intact ophthalmic branch of the trigeminal nerve is neither necessary nor sufficient for good homing performance from unfamiliar locations, but that an intact olfactory nerve is necessary.

Section: Resultsmentioning

confidence: 55%

Having the nerve to home: trigeminal magnetoreceptor versusolfactory mediation of homing in pigeons

Savini

et al. 2006

“…Therefore, the released birds are able to orient towards home using a compass mechanism (Keeton, 1971;SchmidtKoenig, 1961). The strongest evidence in favour of the olfactory navigation hypothesis comes from two main kinds of experimental protocols: (1) the manipulation of the olfactory system in order to prevent odour perception prior to release (Gagliardo et al, 2009;Papi, 1982;Wallraff et al, 1989) and (2) the manipulation of olfactory information, either in terms of odour quality or wind direction at the home loft, aimed at preventing or manipulating map learning (Ioalè et al, 1978;Ioalè et al, 1990;Odetti et al, 2003;Papi et al, 1974;Papi, 1986;Wallraff, 1979). The latter, applied on birds with an intact olfactory system, provided results supporting a specific role of olfactory cues in navigation and contradicting the olfactory activation hypothesis, which attributes to the olfactory stimuli a role in priming a non-olfactory navigational mechanism (Jorge et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Olfactory lateralization in homing pigeons: a GPS study on birds released with unilateral olfactory inputs

Filannino

et al. 2011

SUMMARYA large body of evidence has shown that pigeons rely on an olfactory-based navigational map when homing from unfamiliar locations. Previous studies on pigeons released with one nostril occluded highlighted an asymmetry in favour of the right nostril, particularly concerning the initial orientation performance of naïve birds. Nevertheless, all pigeons experiencing only unilateral olfactory input showed impaired homing, regardless of the side of the occluded nostril. So far this phenomenon has been documented only by observing the birds' vanishing bearings. In the present work we recorded the flight tracks of pigeons with previous homing experience equipped with a GPS data logger and released from an unfamiliar location with the right or the left nostril occluded. The analysis of the tracks revealed that the flight path of the birds with the right nostril occluded was more tortuous than that of unmanipulated controls. Moreover, the pigeons smelling with the left nostril interrupted their journey significantly more frequently and displayed more exploratory activity than the control birds, e.g. during flights around a stopover site. These data suggest a more important involvement of the right olfactory system in processing the olfactory information needed for the operation of the navigational map.

“…As much of the experimental evidence in favour of the olfactory navigation hypothesis was achieved by releasing birds made anosmic with different manipulations involving parts of the upper beak (nostrils, olfactory mucosa) Bingman et al, 1998;Guilford et al, 1998;Wallraff, 1988;Wallraff, 2005;Wallraff et al, 1989), Mora and colleagues (Mora et al, 2004) suggested that the observed navigational impairment following anosmia might have actually been due to accidental damage of the nearby putative magnetic receptor. A recent paper (Gagliardo et al, 2006) overcame this objection to the olfactory navigation hypothesis, by showing that inexperienced homing pigeons with a proximal section of the olfactory nerve that did not involve the beak were unable to navigate, whereas birds subjected to section of the ophthalmic branch of the trigeminal nerve displayed unimpaired orientation and homing performance from unfamiliar locations.…”

Section: Introductionmentioning

confidence: 99%

Navigational abilities of homing pigeons deprived of olfactory or trigeminally mediated magnetic information when young

Savini

et al. 2008

SUMMARYAnatomical evidence and conditioning experiments have recently suggested that magnetoreceptors are located in the upper beak of homing pigeons, where they are innervated by the ophthalmic branch of the trigeminal nerve. These findings have raised the issue of whether the trigeminally mediated magnetoreception is involved in the navigational mechanisms of homing pigeons. Recent data have shown that, in inexperienced pigeons, section of the ophthalmic branch of the trigeminal nerve does not impair navigational abilities, whereas the navigational performance of inexperienced pigeons is disrupted after section of the olfactory nerve. Nevertheless, the issue of whether the stimuli available during development of the navigational mechanism can influence the types of cues used in determining the direction of displacement remains unresolved. To address this issue, we surgically deprived young pigeons of either olfactory or trigeminally mediated magnetic information, and then later tested their navigational abilities subsequent to an intensive training flight program of up to 10 km in different directions. The birds deprived of trigeminally mediated magnetic information when young developed navigational abilities at the same level as intact control pigeons, whereas the olfactory deprived pigeons displayed randomly scattered initial orientation and poor homing performance. Our data show that olfactory cues are needed for the development of navigational abilities from unfamiliar locations and that the lack of magnetic information does not affect the development of homing abilities.