嚙齒類動物群居起源研究假說

衛(wèi)萬榮，麻安衛(wèi)，何凱，張衛(wèi)國*

(1.草地農(nóng)業(yè)生態(tài)系統(tǒng)國家重點實驗室,蘭州大學(xué)草地農(nóng)業(yè)科技學(xué)院，甘肅 蘭州 730020; 2.秦安縣農(nóng)村能源開發(fā)站，甘肅 秦安 741600)

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嚙齒類動物群居起源研究假說

衛(wèi)萬榮1，麻安衛(wèi)1，何凱2，張衛(wèi)國1*

(1.草地農(nóng)業(yè)生態(tài)系統(tǒng)國家重點實驗室,蘭州大學(xué)草地農(nóng)業(yè)科技學(xué)院，甘肅 蘭州 730020; 2.秦安縣農(nóng)村能源開發(fā)站，甘肅 秦安 741600)

摘要：文章闡述了有關(guān)嚙齒類動物群居起源相關(guān)的7個假說。資源防衛(wèi)假說認(rèn)為當(dāng)資源(食物、水、庇護(hù)所)在時空上呈斑塊狀聚集分布時，群居有利于獲取和保護(hù)資源。捕食風(fēng)險假說認(rèn)為群居能降低嚙齒類被捕食的風(fēng)險，因此在高風(fēng)險棲境中群居較為普遍。社群溫度調(diào)節(jié)假說認(rèn)為在寒帶和氣候寒冷的地區(qū)群居有利于嚙齒類減少能量消耗。旱區(qū)食物分布假說認(rèn)為處于干旱生境中的嚙齒類為減少挖掘洞道所需的能耗和弱化無收益覓食風(fēng)險不得不形成群居。生活史約束假說認(rèn)為體型小、脂肪貯存能力低、生長速率慢的嚙齒類為能成功撫育后代而不得不形成群居。由于構(gòu)建洞穴耗能巨大，因此窩巢共享假說認(rèn)為嚙齒類為減少能耗被迫共享洞系進(jìn)而形成群居。親代投資假說認(rèn)為由于親本對后代的持續(xù)性投資，因而群居的形成是由子代推遲擴(kuò)散導(dǎo)致的。最后，本文對嚙齒類群居未來研究的熱點進(jìn)行了探討。

關(guān)鍵詞：群居；資源防衛(wèi)假說；捕食風(fēng)險假說；社群溫度調(diào)節(jié)假說；旱區(qū)食物分布假說；生活史約束假說；窩巢共享假說；親代投資假說

群居(社會性)動物是指以群體為生活方式，無論覓食、休憩、遷移等行為都以集體為單位，彼此間相互關(guān)照，相互協(xié)助的動物[1]。影響動物群居的因素一直是動物社會生物學(xué)和行為生態(tài)學(xué)的研究熱點。動物群居可能由某種自然因素或同一外部刺激對個體吸引而致，也可能是動物個體間相互吸引造成的[2]，亦可能是動物本身的擴(kuò)散受到外部環(huán)境限制導(dǎo)致的[3]。棲息適合度是判定是否有利于動物群居的綜合指標(biāo)，包括捕食風(fēng)險、覓食效率、寄生蟲和疾病傳播、攻擊性、資源競爭、殺嬰和通奸行為等諸多因素[4-8]。只有降低這些弊端和約束產(chǎn)生的影響，棲息適合度適宜，動物才會形成群居生活[9]。

嚙齒類是哺乳動物中種類最多的一個類群，也是分布范圍最廣的哺乳動物，全世界約有2000多種。其生活方式獨居、臨時聚群和群居均有[3,10]。群居嚙齒類是指個體間聯(lián)系頻繁，有共同的攝食區(qū)域、領(lǐng)地，共享一個窩巢和洞系[11-13]。有關(guān)嚙齒類群居理論論述研究我國學(xué)者還未曾有過評述，國外亦不多見[14-15]。因此本文在國內(nèi)外現(xiàn)有文獻(xiàn)的基礎(chǔ)上，介紹影響嚙齒類群居起源的主要觀點及相關(guān)研究，如資源防衛(wèi)假說(the resource-defense hypothesis)、捕食風(fēng)險假說(the predatory risk hypothesis)、溫度調(diào)節(jié)假說(the social thermoregulation hypothesis)、旱區(qū)食物分布假說(the aridity food-distribution hypothesis)、生活史限制假說(the life-history constraint hypothesis)、親代投資假說(the parental investment hypothesis)、窩巢共享假說(the burrow-sharing hypothesis)，對相關(guān)研究進(jìn)行總結(jié)評價，并對未來的研究熱點進(jìn)行探討，為我國學(xué)者提供參考。

1資源防衛(wèi)假說

資源防衛(wèi)假說又稱資源分散假說(the resource dispersion hypothesis)：當(dāng)資源(食物、水、庇護(hù)所、配偶)在時空上呈斑塊狀分布，群居有利于嚙齒類獲取和保護(hù)資源[15]。簡明而言，個體所能獲取的資源隨種群數(shù)量增加而增加，嚙齒類種群密度隨資源聚集程度的增加而增加；反之，資源稀疏且均勻分布時，保護(hù)資源所需代價巨大，棲息適合度降低，群居就顯得不切實際[16]。

許多實驗性研究結(jié)果與該假說相符。例如，人為控制甘尼森土撥鼠(Cynomysgunnisoni)食物后其種群與社群結(jié)構(gòu)發(fā)生改變[16]。當(dāng)食物聚集度增加后土撥鼠攝食區(qū)域減小，種群密度增加；反之食物減少且分布均勻時其攝食區(qū)域擴(kuò)大，種群密度降低。野外觀測實驗也得到了相同結(jié)果[17-19]。在食物集中分布的區(qū)域，土撥鼠種群密度較大；但在食物聚集度低并均勻分布的區(qū)域，種群密度較?。辉黾哟菩宰乇呈笃絒17](Clethrionomysrufocanus)和雌性加利福尼亞小田鼠[18](Microtuscalifornicus)食物資源后二者活動范圍的重疊度顯著增加；實驗性增加雌性棕背鼠平數(shù)量后聚群現(xiàn)象明顯增加[19]。除此而外，攝食領(lǐng)域亦隨種群大小而變，如長爪沙鼠[20](Merionesunguiculatus)和水豚[21](Hydrochaerishydrochaeris)個體所能獲取的資源隨領(lǐng)地增大而增加。由于食物對鼠類能否生存和成功繁殖至關(guān)重要，增加尾林鼠[22](Neotomacinerea)和巖豚鼠[23](Kerodonrupestis)的食物后，其種群內(nèi)有更多的個體參與到儲存和保護(hù)食物資源的過程中，亦從側(cè)面驗證了該假說。

盡管許多研究支持該假說，但亦有研究與該假說相矛盾，如阿根廷長耳豚鼠(Dolichotispatagonum)，其群居的形成僅僅是由于旱季食物資源短暫性聚集分布導(dǎo)致的，其他季節(jié)食物資源零星分布時并不形成群居[24]；人為增加雌性或雄性黑田鼠[25](Microtusagrestis)后其社群結(jié)構(gòu)并不改變；旱獺[26](Marmotacaudata)的種群大小與可利用食物資源無相關(guān)性。

2捕食風(fēng)險假說

捕食風(fēng)險指動物為躲避捕食者而改變其行為方式和生理狀態(tài)付出的代價[27]。行為改變包括：活動模式和時間分配格局的改變[28-29]；具體表現(xiàn)為選擇相對安全但食物質(zhì)量低的棲境[30-31]、減少取食頻率和時間而相應(yīng)地增加警覺時間[32-36]、增加對環(huán)境條件的敏感性[37]、增加間斷性移動模式、食物選擇及食譜改變[38]。嚙齒類降低捕食風(fēng)險主要通過以下幾種機(jī)制：1、多眼效應(yīng)(the‘many eyes effect’)；2、自私的獸群效應(yīng)(the‘selfish herd effect’)；3、增加種群防御；4、稀釋效應(yīng)(the dilution effect)。多眼效應(yīng)認(rèn)為密度大的種群更易發(fā)現(xiàn)捕食者；自私的獸群效應(yīng)認(rèn)為捕食風(fēng)險與其所處種群的位置相關(guān)(通常棲境外圍的個體被捕食的風(fēng)險較高)；稀釋效應(yīng)最為簡單，捕食風(fēng)險隨種群密度增加而降低(因種群數(shù)量增加每個個體被捕食的概率下降)；種群防御機(jī)制(尤其對于攻擊性強的嚙齒類而言)認(rèn)為能否成功擊退捕食者與參與到防御中的個體數(shù)量相關(guān)。因此，捕食風(fēng)險假說認(rèn)為在高風(fēng)險棲境中嚙齒類群居普遍，同時捕食風(fēng)險與棲境中植被高度、蓋度密切相關(guān)[39]。

多眼效應(yīng)認(rèn)為捕食風(fēng)險隨種群大小而變。許多嚙齒類行為學(xué)相關(guān)研究驗證了這一點，如隨著灌叢八齒鼠(Octodondegus)種群密度的增加，其發(fā)現(xiàn)人類捕食者的時間越早[40]；高原鼠兔覓食時間隨種群數(shù)量增加而上升，相反，其警戒和洞內(nèi)時間卻隨種群密度增加而減少[35]；除此而外，群居的田鼠(Microtusepiroticus)、棕背鼠平(Clethrionomysglareolus)和黃姬鼠(Apodemusflavicollis)被鼬襲擊和獵殺的概率要低于獨居個體[41]；種群密度大的黑尾草原犬鼠(Cynomysludovicianus)和白尾草原犬鼠(Cynomysleucurus)相比小種群而言能夠較早發(fā)現(xiàn)天敵從而進(jìn)行有效躲避[42]。但亦有研究結(jié)果并不支持捕食風(fēng)險假說，如Hayes等[43]發(fā)現(xiàn)灌叢八齒鼠種群大小與其存活率并無明顯相關(guān)性。

黑尾草原犬鼠[44]、旱獺[45]和水豚[46]的行為研究驗證了自私的獸群效應(yīng)，相比核心區(qū)域的個體而言，領(lǐng)域外圍的個體通常所需的警戒時間較長、警戒頻率更高；另外，降低草原犬鼠密度后發(fā)現(xiàn)中央?yún)^(qū)域位置附近覓食的個體數(shù)明顯增加，外圍個體數(shù)減少[47]。

捕食風(fēng)險與種群內(nèi)的個體數(shù)量緊密相關(guān)，種群密度大時個體活動區(qū)域擴(kuò)大[48]。草原犬鼠覓食區(qū)域與洞口距離的遠(yuǎn)近和種群密度密切相關(guān)，從一定程度上驗證了稀釋效應(yīng)。這是因為捕食風(fēng)險隨種群密度增加而降低，相應(yīng)的其活動范圍就會擴(kuò)大。

種群防御機(jī)制在野外觀察中得到了證實。群居能減少被天敵襲擊的概率，如水豚群居可減少野狗侵襲其幼崽[49]；除此而外，還能有效地阻止同類入侵者，如雌性小家鼠[50](Musmusculus)和貝爾丁地松鼠[51](Spermophilusbeldingi)群居可降低同類入侵引起的殺嬰行為。

嚙齒類行為學(xué)和生態(tài)學(xué)相關(guān)研究表明植被蓋度與捕食風(fēng)險顯著相關(guān)。自然生境中，有些嚙齒類如長爪沙鼠[20](Merionesunguiculatus)、高原鼠兔[52](Ochotonacurzoniae)和豚鼠[53](Caviaaperea)在植被稀疏低矮的生境密度大，而另一些如布氏田鼠[54](Microtusbrandti)、白尾草原犬鼠[42]多棲息于植被蓋度大的生境，造成這種生境的差異是嚙齒類長期與自然環(huán)境相適應(yīng)的結(jié)果。白足鼠(Peromyscusleucopus)、灰松鼠(Sciuruscarolinensis)和花栗鼠(Tamiasstriatus)在開闊生境中覓食時間減少，警戒時間顯著增加[15]。捕食風(fēng)險與植被蓋度的關(guān)系在人為控制實驗中也得到了驗證。相比植被蓋度低的生境而言，加氏鹿鼠[55](Clethrionomysgapperi)和小沙鼠[56](Gerbilluspyramidum)在植被蓋度大的生境中受到襲擊的概率較低；降低草原犬鼠密度后其會盡量避免棲息于開闊生境[57]。

雖然植被蓋度與捕食風(fēng)險的關(guān)系得到了驗證，但仍受到許多不可控制因素的影響。首先，植被能在視覺上阻礙天敵發(fā)現(xiàn)獵物的幾率[58]；其次，與植被蓋度相關(guān)的安全性與天敵類型有關(guān)[59]。如增加植被蓋度會減少被飛禽類天敵發(fā)現(xiàn)的幾率，但被爬行類捕食者發(fā)現(xiàn)的幾率增加[60]；再者，許多嚙齒動物用鳴聲和視覺(豎起尾巴)信號向同類傳遞風(fēng)險信號，植被是否有利于聲音和視覺信號傳遞取決于植被高度和聲音的頻率[42]。關(guān)于捕食風(fēng)險對嚙齒類種群的研究表明，捕食風(fēng)險效應(yīng)不但是影響獵物種群動態(tài)的一個重要因素，其對獵物種群動態(tài)的調(diào)控作用可能要大于直接捕殺[27]。

3社群溫度調(diào)節(jié)假說

社群溫度調(diào)節(jié)假說又稱為能耗調(diào)節(jié)假說：在寒帶和氣候寒冷的地區(qū)，嚙齒類為減少能耗、增加生存幾率就會形成群居[61-62]，個體的能量耗損與群居的數(shù)量呈負(fù)相關(guān)性[62]。有3種機(jī)制能解釋小型動物蜷縮擠在一起降低能耗：1)減少暴露在空氣中的體表面積有利于減少新陳代謝速率進(jìn)而利于保存能量[63]；2)洞穴中濕度和溫度的增加會減少動物熱量和水分損耗[40]，因此環(huán)境濕度和溫度的增加[64]利于體溫調(diào)節(jié)；3)某些生理過程能調(diào)節(jié)體溫[62]。

在室內(nèi)條件下證實了動物緊緊擁簇可降低能耗、增加生存概率這一點，如裸鼢鼠[65](Heterocephalusglaber)、長爪沙鼠[66]、麝鼠[67](Ondatrazibethicus)、八齒鼠[64]、達(dá)馬拉蘭鼴鼠[68](Cryptomysdamarensis)、納塔爾摩爾鼠[68](Cryptomyshottentotusnatalensis)和家兔[69](Oryctolaguscuniculus)等。野外觀察結(jié)果也得出相同結(jié)論，當(dāng)冬季來臨時，南部飛鼠[70](Glaucomysvolans)、灰松鼠[71]、草原田鼠[72](Microtuspennsylvanicus)和紋鼠[73](Rhabdomyspumilio)單位洞系中的個體數(shù)明顯增加；除此而外，鼠類的冬季存活率隨窩巢內(nèi)個體數(shù)量增加而增大、體重?fù)p耗量下降[74-75]亦從側(cè)面驗證了該點。

但也有一些室內(nèi)和野外試驗并不支持該假說，如草原犬鼠的能耗與季節(jié)變化無關(guān)，無顯著差異[76]；低溫環(huán)境下獨居的西伯利亞倉鼠(Phodopussungorus)和群居相比，盡管群居個體脂肪量較高、體況較好，但二者能耗并無明顯區(qū)別[77]；另外，冬眠性的黃腹土撥鼠(M.flaviventris)其群居性的亞成體平均日損耗量要大于獨居個體也與該假說相矛盾[78]。

4旱區(qū)食物分布假說

Jarvis和Sherman[79]提出了旱區(qū)食物分布假說，該假說能夠很好地解釋干旱地區(qū)地下鼠形成群居的機(jī)制。由于地下鼠所處生境降水量小，土壤硬度大、食物呈簇狀分布，因而地下鼠易形成群居。干旱生境中地下鼠群居有利于降低覓食成本，覓食成本包括挖掘洞道所耗能量和無收益覓食風(fēng)險[80]。無收益覓食風(fēng)險指到達(dá)食物分布區(qū)域過程中可能面臨無任何食物獲取而必須承擔(dān)的風(fēng)險[81]。干旱生境中食物資源呈斑塊狀聚集分布，由于地下鼠覓食無方向性，再加上地下覓食是高耗能活動[79-80,82-83]，獨居地下鼠常會因為不能及時發(fā)現(xiàn)足夠維持自身生存的食物而導(dǎo)致無收益覓食風(fēng)險增加，合作覓食有2個好處：1)發(fā)現(xiàn)食物的幾率增加，2)減少單位個體能耗。

干旱生境會限制地下鼠的擴(kuò)散，影響種群形成以及覓食的有效性。如干旱生境中隱鼠[84](Cryptomyshottentotushottentotus)種群的遷入率和遷出率要低于濕潤地區(qū)，種群結(jié)構(gòu)穩(wěn)定；食物資源與洞系分形維數(shù)正相關(guān)，非洲鼴鼠[83](Fukomysmechowii)雨季洞系的分形維數(shù)和所能獲取的食物資源要高于旱季，并且同一季節(jié)大種群的分形維數(shù)要大于小種群，說明大種群能增加覓食有效性；達(dá)馬拉蘭鼴鼠(Cryptomysdamarensis)的小種群生存下來的概率要低于大種群[82]；除此而外，計算機(jī)模擬發(fā)現(xiàn)食物的簇狀分布與土壤硬度緊密相關(guān)，干旱生境中獨居物種覓食效率低下，而群居形成的合作覓食可降低無收益覓食風(fēng)險[85]。

另外，還能從生理學(xué)角度解釋該假說。群居形成的前提條件是個體的社會容忍度(寬容度)高，這對于那些攻擊性強的物種尤為重要[86]，由于攻擊行為極其耗能和耗水[87]，因此處于旱區(qū)嚙齒類的群居很有可能是其為防止水分和能量損耗而減少攻擊行為的副產(chǎn)物。攻擊性程度與糖皮質(zhì)激素水平正相關(guān)，對鼴鼠和豚鼠生物學(xué)、生態(tài)學(xué)和行為學(xué)方面的研究亦能解釋該點[87-88]。

亦有研究與該假說相矛盾，如棲息于干旱生境中獨居的霜鼠[89](Heliophobiusargenteocinereus)在食物質(zhì)量低的棲境中亦能生存。

5生活史約束假說

Burda和Kawalika[90]提出了生活史約束假說，又有學(xué)者將其稱為“共同撫養(yǎng)后代受益”假說[43](‘benefits of communal care’hypothesis)。該假說認(rèn)為那些體型小、脂肪貯存能力低、生長速率慢的嚙齒類為能成功繁衍后代不得不形成群居。體型小的獨居嚙齒類不能成功撫育后代[90]主要是因為體型小的物種發(fā)育速率緩慢，性成熟周期長，哺乳期雌性沒有足夠的脂肪撫養(yǎng)后代，因此需要很多成體參與撫育后代。達(dá)馬拉蘭鼴鼠和裸鼴鼠是濱屬科體型最小的物種，它們的發(fā)育時間很長就驗證了該假說[82,91-92]。共同撫育后代有諸多優(yōu)點，如增強后代免疫功能[93]、減少寄生蟲和病菌的感染幾率[94]，增強個體調(diào)控體溫的能力[72]。

然而，Bennett等[95]活捕解剖哺乳期獨居的雌性岬鼠(Georychuscapensis)和4種社會性的雌性隱鼠，發(fā)現(xiàn)均有脂肪堆積的現(xiàn)象，這與生活史約束假說矛盾。

6窩巢共享假說

群居與動物的生命周期、領(lǐng)域擴(kuò)張及棲境的安全緊密相關(guān)[96]，大多數(shù)嚙齒類將洞系和窩巢作為規(guī)避極端天氣、儲存食物和冬眠的場所[97]，因而洞系對嚙齒類而言是一種極為關(guān)鍵重要的資源。由于天然避難所有限，而建造洞系對個體而言代價巨大，因而動物被迫共享洞系進(jìn)而形成群居[98-99]。該假說認(rèn)為構(gòu)建洞穴的嚙齒類更易形成群居。

自King[100]發(fā)現(xiàn)洞系資源與嚙齒類社會制度緊密相關(guān)后，許多學(xué)者對此做了大量研究。如匈牙利小家鼠(Musspicilegus)在秋季建造土冢時(繁殖場所)，由于建造土冢耗能巨大，個體并不能單獨完成，因此需要很多個體參與，最后共享洞系形成群居[101]；洞系亦是決定八齒鼠群居的關(guān)鍵因素[7,101]；相比小種群而言，較大種群的八齒鼠能利用更多洞系資源[90]；草原犬鼠獨居和群居均有，但群居的洞系構(gòu)造要比獨居的復(fù)雜[76]。

盡管很多研究結(jié)果支持該假說，但亦有很多實驗結(jié)論與之相悖。如相比獨居的灌叢八齒鼠，群居并不會減少洞系建造的時間，這與洞系共享假說不符[99]，但相比獨居而言，群居個體平均推至地表的土壤要多，從長遠(yuǎn)來看，群居有利于其減少建造洞系所付出的代價；除此而外，亦有研究表明洞系資源并非是限制灌叢八齒鼠群居形成的真正原因[102]；構(gòu)筑洞系的豚鼠比不構(gòu)筑洞系的更易形成較大的種群[103]；水鼠平(Arvicolaterrestris)嚴(yán)重依賴洞道作為逃避捕食者的場所，盡管洞系建造成本較高，水鼠平也不會為分享洞道而形成群居[104]；小豚鼠[105](Microcaviaaustralis)群居形成的真正原因并不是為減少能耗；還有許多獨居地下鼠行為學(xué)研究結(jié)果與該假說相矛盾[12-13,106]。

7親代投資假說

該假說認(rèn)為群居是斷奶后親本持續(xù)性投資[107]致使子代推遲擴(kuò)散導(dǎo)致的[108-110]。因而體型大的物種擴(kuò)散延遲的可能性更大，因為即使食物充足，也要很長時間才能發(fā)育完全[107,109]。

群居嚙齒類發(fā)育成熟所需的時間和擴(kuò)散的時間呈正相關(guān)，而與生長季長短負(fù)相關(guān)。如溫帶地區(qū)松鼠生長周期的長短與積雪消融時間呈負(fù)相關(guān)。北美松鼠的生物學(xué)研究驗證了親代投資假說[111]；生長周期長的土撥鼠發(fā)育成熟的時間早，擴(kuò)散時間早[112]。也有實驗結(jié)論與之矛盾，如北美土撥鼠(Marmotamonax)的社會性并不隨生長季的長短發(fā)生變化[75]；高山土撥鼠在亞成體階段因食物因素不得不擴(kuò)散[91]。

8小結(jié)

許多假說均能一定程度上解釋嚙齒類群居的原因，同時它們之間也并不相互排斥。例如，嚙齒類群居既能夠減少捕食風(fēng)險，也能通過體溫調(diào)節(jié)減少能耗。因此，在未來研究嚙齒類群居因素時須考慮各個假說。例如，有些學(xué)者研究的焦點可能限制于旱區(qū)食物分布假說和生活史約束假說，然而，捕食風(fēng)險假說和資源防衛(wèi)假說有時卻可能更為恰當(dāng)。

嚙齒類群居是綜合考慮環(huán)境和自身因素利弊權(quán)衡后的結(jié)果。首先，群居并非是某個因素單獨引起的，可能是很多因素綜合作用導(dǎo)致的；其次，影響動物群居的決定性因素是隨動物不斷適應(yīng)環(huán)境而變的，并非是一成不變；第三，與種群相關(guān)的其他社會屬性如數(shù)量、社群關(guān)系的穩(wěn)定性仍不清楚。以上3點需更復(fù)雜、精細(xì)、長周期的實驗來驗證。

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The evolutionary causes of rodent group-living: Hypotheses

WEI Wan-Rong1, MA An-Wei1, HE Kai2, ZHANG Wei-Guo1*

1.StateKeyLaboratoryofGrasslandAgro-ecosystems,CollegeofPastoralAgriculturalScienceandTechnology,LanzhouUniversity,Lanzhou730020,China; 2.RuralEnergyDevelopmentStationofQin’an,Qin’an741600,China

Abstract:This paper describes 7 hypotheses concerning group-living rodents which are accepted by most researchers. The resource-defense hypothesis believes that group-living individuals may become more efficient in obtaining and protecting resources than solitary-living conspecifics when resources (food, water, shelter) are non-uniformly distributed. The predatory risk hypothesis states that sociality should prevail in riskier habitats because group-living can reduce the risk of predation. The social thermoregulation hypothesis suggests that group-living could reduce the energy consumption in relatively cold habitats. The aridity food-distribution hypothesis believes that rodents living in arid habitats live in groups to share burrows or minimize the cost of burrow construction. The life-history constraint hypothesis thinks that rodents with smaller size, lower fat reserves, and low rate of postnatal growth are forced to live in groups to be able to successfully foster offspring. The burrow-sharing hypothesis states that rodents are forced to live in groups to share burrow use or minimize the cost of burrow construction. The parental investment hypothesis believes that, because of the continuing investment in offspring, group-living resulted from delay dispersion of offspring. Finally the paper discusses the future research focus on rodent group-living.

Key words:group-living; the resource-defense hypothesis; the predatory risk hypothesis; the social thermoregulation hypothesis; the aridity food-distribution hypothesis; the life-history constraint hypothesis; the burrow-sharing hypothesis; the parental investment hypothesis

*通信作者

Corresponding author. E-mail: wgzhang@lzu.edu.cn

作者簡介：衛(wèi)萬榮(1988-)，男，甘肅皋蘭人，在讀博士。E-mail:weiwr07@lzu.edu.cn

基金項目：公益性行業(yè)項目(201203041)資助。

*收稿日期：2015-11-17；改回日期：2015-12-28

DOI：10.11686/cyxb2015520

http://cyxb.lzu.edu.cn

衛(wèi)萬榮， 麻安衛(wèi)， 何凱， 張衛(wèi)國. 嚙齒類動物群居起源研究假說. 草業(yè)學(xué)報, 2016, 25(4): 212-221.

WEI Wan-Rong, MA An-Wei, HE Kai, ZHANG Wei-Guo. The evolutionary causes of rodent group-living: Hypotheses. Acta Prataculturae Sinica, 2016, 25(4): 212-221.