The sight of tens of thousands of flamingos flocking together to create a huge pink cloud may be one of the wonders of the natural world but research suggests that within these vast congregations, individual birds form intimate, long-lasting friendship groups.
A five-year study of captive flocks in Gloucestershire has found that flamingos spend large amounts of time with specific close “friends” in groups of up to four or five. The report says that some of these friendship groups appear to avoid others they do not get along with. No loners were spotted but some individuals, dubbed “social butterflies” by the researchers, did flit from group to group.
It has long been known that gatherings of flamingos in the wild, which can number up to two million individuals, are complex social structures. It is also known that the birds have very different individual characteristics. Some are pushy and aggressive, barging their way into the middle of the best feeding areas, while others are quieter, feeding around the edge and trying to not get in other flamingos’ way. But there are many mysteries, including how long pairs stick together.
Photo: AFP 照片:法新社
Scientists from the University of Exeter studied about 350 birds, comprising four species, at the WWT Slimbridge wetland center. The researchers have not yet been able to establish how long pairs mate for but did spot consistent friendship groups.
Paul Rose, a zoologist and ornithologist, said: “Our results indicate that flamingo societies are formed of long-standing friendships rather than loose, random connections.” “Flamingos don’t simply find a mate and spend their time with that individual. We see pairs of males or females choosing to hang out, we see trios and quartets that are regularly together.” “Flamingos have long lives — some of the birds in this study have been at Slimbridge since the 1960s — and our study shows their friendships are stable over a period of years. It seems that, like humans, flamingos form social bonds.”
The study could not establish how long pairs mate for but did spot consistent “friendship” groups. Previous studies have found strong social networks in species ranging from zebra finches to red jungle fowl. The vastness of flamingo groups in the wild means it is hard to study individuals or groups.
Photo: EPA-EFE 照片:歐新社
For the Gloucestershire study, ringed birds were photographed between three and four times a day to establish which were sticking together. The friendship groups identified contained between two and five individuals and were inevitably both male and female. The study examined flocks of Caribbean, Chilean, Andean and lesser flamingos at the wetland center. The flocks varied in size from just over 20 to more than 140.
It found that seasons affected social interactions, with more bonds forming in spring and summer — the breeding season. But the health of the birds did not seem to matter. They maintained their groupings even if one of them was not in tip-top condition.
Rose said sticking together in smaller groups could help the individuals find food, keep an eye out for predators and know when the whole flock was about to move. He believes the same sort of social groupings identified at Slimbridge would happen in the wild and understanding the birds’ inter-flock relationships could help conservation work.
More immediately it may inform how flamingos in captivity are cared for. “When moving birds from one zoo to another, we should be careful not to separate flamingos that are closely bonded to each other,” he said. The findings are published in the journal Behavioural Processes.
(The Guardian)
數以萬計的紅鶴聚在一起、形成一片巨大的粉紅色雲彩,如此景象可說是自然世界的一幅壯麗奇景,不過研究指出,在這些大規模集會中,個別的紅鶴也會組成親密且友誼長存的小團體。
關於英國格洛斯特郡圈養紅鶴群體的一份五年期研究發現,這種鳥類會花上大量時間和特定的紅鶴「知己」相處,組成小團體的紅鶴數量則多達四到五隻。報告指出,有些友誼團體的組成原因似乎是為了避免和其他不對盤的紅鶴相處。在觀察過程中,研究人員並未發現「紅鶴獨行俠」,不過某些被研究人員稱為「交際花」的紅鶴個體卻會翩然穿梭在不同團體間。
科學家很早就發現野外紅鶴的大型集會──數量可上看兩百萬隻──含有複雜的社會結構,也知道這種鳥類彼此個性迥然相異。有些紅鶴強勢且帶有侵略性,經常魯莽地衝進最好的覓食區中間;有些紅鶴則比較安靜,會在周圍覓食,盡量不要擋到其他紅鶴的路。儘管如此,還是有許多謎團尚未解開,例如一對紅鶴會在一起多久。
英國艾希特大學的科學家在「野禽與濕地信託基金會」的斯林布里奇溼地中心內,對四種紅鶴共三百五十隻個體進行研究。研究人員仍無法確定一對紅鶴會維持伴侶關係多久,不過他們卻發現穩定維持的友誼團體。
動物學家、同時也是鳥類學者的保羅‧羅斯指出:「我們的研究結果顯示,紅鶴社會是由穩固的友誼所形成,而非鬆散、隨機的來往關係。」他表示:「紅鶴並不會輕易地找配偶,就這樣跟對方共度時光。我們看到的是,一對一對的公鳥或母鳥選擇一起閒晃,也看到三隻或四隻經常一起行動的組合。」他進一步指出:「紅鶴生命很長──這份研究裡面甚至有些個體從一九六○年代就待在斯林布里奇(溼地中心)了,而我們的研究顯示,紅鶴的友情穩定持續了好幾年。看起來,紅鶴就像人類一樣,會形塑社會聯繫。」
雖然該研究無法肯定一對紅鶴會在一起多久,但是他們卻觀察到穩定的友誼團體。之前的研究曾經許多物種中發現堅固的社會網絡存在,其中包括斑胸草雀以至於紅色原雞(譯註:目前多數學者認為的家雞祖先)等多樣物種。然而,野外紅鶴群體的規模十分龐大,使得研究個體或族群相當困難。
在這份格洛斯特郡的研究中,研究人員對戴有識別腳環的紅鶴們一天拍上三到四次照片,確認出哪幾隻經常黏在一起活動。他們辨識出的友誼團體通常包含兩隻到五隻個體,而且一定同時有公母。該研究檢驗的對象為溼地中心內的加勒比海紅鶴(又稱美洲紅鶴)、智利紅鶴、安第斯紅鶴、以及小紅鶴。鳥群的大小各不相同,有的二十隻,有的超過一百四十隻。
研究同時發現,季節會影響紅鶴的社會互動,春夏兩季──也就是繁殖季──通常會形成較多組社會聯繫。另一方面,它們的健康狀況似乎不會對社交帶來影響。就算其中一隻並不在絕佳狀態,火鶴們還是會維繫自己的團體。
羅斯表示,一起待在小集團裡面可以幫助紅鶴個體找尋食物、注意掠食者、並且知道整個群體什麼時候會開始移動。羅斯相信,他們在斯林布里奇辨識出的社會性聚集行為同樣會出現在野外群體中,而且,了解這些鳥類在群體內部發展出的關係有助於保育工作。
這項觀察最立即的影響在於提供圈養紅鶴更好的照顧方式。羅斯指出:「當我們要把紅鶴搬去另一間動物園時,應該要小心不要分開那些彼此緊密相繫的紅鶴們。」這份研究日前刊登在期刊《Behavioural Processes》。
(台北時報章厚明譯)
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