科學家研究發現鴿子腦內有與生俱來的空間圖

The mystery of how a pigeon can always find its way back home has finally been solved.

Scientists believe that pigeons have a spatial map that allows them to fly in an unfamiliar territory and know exactly where they are going.

The finding replaces the current theory that pigeons compare the coordinates of their location with those of the home loft and then systematically reduce the difference between the two to find their way home.

This earlier theory likens the navigation of pigeons to that of flying robots.

But experiments carried out at the University of Zurich have shown that pigeons possess cognitive capabilities.

In unknown areas, the scientists claim pigeons recognise where they are in relation to their home loft and are able to choose their targets themselves.

Homing pigeons and migratory birds determine their flight direction with the help of the Earth’s magnetic field, the stars and the position of the sun.

Nicole Blaser, a doctoral student in biology at the University of Zurich proposed the theory that pigeons have a spatial understanding and knowledge of their position in space relative to their home loft.

This theory presupposes a type of mental map in their brain and thus cognitive capabilities. Up until now, there has not been any clear evidence to support this.

For their experiments, Blaser and her colleagues fitted homing pigeons with miniature GPS loggers in order to monitor the birds’ flight paths.

Beforehand the researchers trained the pigeons not to obtain food in the home loft, as was normally the case otherwise.

‘We fed the pigeons in a second loft around thirty kilometres away, from where they each had to fly back to their home loft’, said Blaser, explaining the structure of the experiment.

The scientists then brought the pigeons to a third place unknown to the pigeons in completely unfamiliar territory.

This release site was in turn 30 kilometres from the home loft and the food loft. Natural obstacles obscured visual contact between the release site and the two lofts.

One group of the pigeons was allowed to eat before flying home. The other group was kept hungry before starting off.

‘We wanted to find out whether the hungry pigeons fly first to the home loft and from there to the food loft or whether they are able to fly directly to the food loft,’ said Blaser.

‘As we expected, the satiated pigeons flew directly to the home loft’, said professor Hans-Peter Lipp, neuroanatomist at the University of Zurich.

‘They already started on course for their loft and only deviated from that course for a short time to make topography-induced detours.’

The hungry pigeons behaved differently, setting off on course for the food loft from the very beginning and flying directly to that target.

They also flew around topographical obstacles and then immediately adjusted again to their original course.

Based on this evidence, Blaser believes that pigeons can determine their location and their direction of flight relative to the target and can choose between several targets.

Blaser concluded that pigeons have a type of cognitive navigational map in their heads and have cognitive capabilities.

‘Pigeons use their heads to fly’, she said.據英國《每日郵報》7月26日報道，瑞士蘇黎世大學的科學家經過實驗得出結論：鴿子大腦中有一幅空間地圖，因而能夠在陌生地區飛行，並能判斷出確切的飛行方向。

現有理論認爲，鴿子把自己所處的位置座標與家裏的鴿房座標相比較，有條理地減小兩者之間的區別，進而找到回家的路。以往的研究認爲，信鴿和候鳥在地球磁場、星星和太陽位置的幫助下確定飛行方向。而蘇黎世大學生物學博士尼科爾•布萊澤則提出新的理論：鴿子具有空間識別能力，知道自己相對於鴿房的空間位置。該理論預先假定鴿子的大腦中有一種意象圖，因而具有認知能力。在此之前，沒有任何顯著證據支持這一理論。

在實驗中，布萊澤和同事在信鴿身上安裝了微型GPS記錄器，以便監測其飛行路線。

與以前的實驗不同，研究人員預先訓練鴿子不在自己的鴿房內獲取食物。“我們在大約30公里外的另一個鴿房喂鴿子，每隻鴿子都必須從那裏飛回自己的鴿房，”布萊澤解釋說。接着，科學家把鴿子帶到距離鴿房和餵食鴿房30公里外的陌生地點，讓自然障礙物模糊了放飛地點與這兩個鴿房之間的視覺接觸。

一組鴿子獲准在回家之前吃東西。另一組鴿子則在出發前保持飢餓。布萊澤說：“我們想弄清楚，飢餓的鴿子是先飛到自己的鴿房再從那裏飛到餵食鴿房，還是可以直接飛到餵食鴿房。”

“正如我們所料，吃飽的鴿子直接飛回了鴿房，”蘇黎世大學神經解剖學教授漢斯-彼得•利普說，“它們已經開始朝鴿房方向飛了，只是在地形誘導下，短時間偏離航線，繞了點路。”飢餓鴿子的行爲則有所不同，它們從一開始就朝餵食鴿房的方向飛，直接飛向了目標。

據此，布萊澤認爲鴿子可以確定自己的位置和相對於目標的飛行方向，而且能夠在幾個目標之間做出選擇。她由此得出結論，鴿子的腦袋裏有一種認知導航地圖，也具有認識能力。