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Der Perote-Ziesel (Xerospermophilus perotensis, Syn.: Spermophilus perotensis) ist eine Hörnchenart aus der Gattung Xerospermophilus. Er lebt ausschließlich in einem abgegrenzten Gebiet in Zentralmexiko.
Der Perote-Ziesel erreicht eine Kopf-Rumpf-Länge von etwa 24,3 bis 26,1 Zentimetern, der Schwanz wird etwa 57 bis 78 Millimeter lang und ist damit deutlich kürzer als der restliche Körper. Die Tiere haben eine gräulich melierte gelbbraune Rückenfärbung mit einer Zeichnung aus dünnen und unterbrochenen schwarzen Streifen. Nach dem Fellwechsel besitzen sie zudem helle, sandfarbene Flecken oder Punkte im Fell. Auffällig sind die weißen Augenlider. Die Füße und die unteren Bereiche sowie das Bauchfell sind blass sandfarben. Die Oberseite des Schwanzes entspricht der Rückenfärbung und wird zum Schwanzende schwarz, die Unterseite ist ocker- bis sandfarben mit einer deutlich erkennbaren schwarzen Linie nahe der Schwanzspitze.[1]
Der Perote-Ziesel ist endemisch im zentralen Mexiko in den Bundesstaaten Veracruz und Puebla. Das Verbreitungsgebiet ist dabei auf etwa 2.500 km2 in den Höhenlagen von 2,200 to 2,700 Metern begrenzt.[1]
Der Perote-Ziesel ist tagaktiv und lebt in trockenen, wüstenartigen Hochebenen im Bereich von offenen Kiefernbeständen und Geröllflächen.[1] Er ist omnivor und die Nahrung besteht wie bei anderen Erdhörnchen vor allem aus verschiedenen Pflanzenteilen sowie Samen und Insekten.
Die Tiere leben wie andere Erdhörnchen am Boden und in unterirdischen Bauen. Die Aktivität der Tiere reicht vom März bis November. Vom November bis zum Frühjahr überwintern sie für drei bis vier Monate in ihren Bauen. Die erwachsenen Männchen erwachen in der Regel vor den Weibchen und den Jungtieren des Vorjahres und verlassen ihre Baue.[1] Die Paarungszeit beginnt nach dem Erwachen der Weibchen vom April bis Mai und tragende Weibchen können bis August vorkommen. Die Jungtiere werden im Bau geworfen, dabei sind bis zu sieben Jungtiere und eine mittlere Wurfgröße von vier Jungtieren dokumentiert.[2] Sie kommen ab Juli aus den Bauen. Die erwachsenen Tiere bereiten sich im späten September bis Oktober auf die Überwinterung vor und bleiben danach in ihren Bauen, die Jungtiere des Jahres kommen bis November an die Oberfläche und überwintern danach.[1]
Die wichtigsten Fressfeinde für den Perote-Ziegel sind wahrscheinlich Haushunde sowie das Langschwanzwiesel (Mustela frenata).[2][1]
Mojave-Ziesel (X. mohavensis)
Rundschwanzziesel (X. tereticaudus)
Perote-Ziesel (X. perotensis)
Fleckenziesel (X. spilosoma)
Der Perote-Ziesel wird als eigenständige Art innerhalb der Gattung der Xerospermophilus eingeordnet, die aus vier Arten besteht. Die Art wurde lange als Teil der Ziesel und darin innerhalb der Untergattung Ictidomys eingeordnet, nach einer umfassenden molekularbiologischen Untersuchung[4] wurde sie jedoch der nun eigenständigen Gattung Xerospermophilus zugeordnet.[5][1] Die wissenschaftliche Erstbeschreibung stammt von dem amerikanischen Zoologen Clinton Hart Merriam aus dem Jahr 1893. Er beschrieb die Art als Spermophilus perotensis anhand von Individuen aus der Region um Perote im mexikanischen Bundesstaat Veracruz.[6][2]
In einer phylogenetischen Untersuchung mit einem Fokus auf die Verwandtschaft des Perote-Ziesels wurde der Fleckenziesel als Schwesterart des Perote-Ziesels identifiziert und den beiden anderen Arten der Gattung, dem Mojave-Ziesel und dem Rundschwanzziesel, gegenübergestellt.[3] Innerhalb der Art werden neben der Nominatform keine Unterarten unterschieden.[1][6]
Der Perote-Ziesel wird von der International Union for Conservation of Nature and Natural Resources (IUCN) als bedroht (endangered) eingeordnet.[7] Begründet wird dies durch das stark begrenzte Verbreitungsgebiet mit einer Fläche von weniger als 5.000 km2 sowie die starke Fragmentierung und die qualitative Verschlechterung der Lebensräume für die Hörnchen.[7]
Die Hauptgefährdung für die Tiere geht von der Umwandlung ihrer Lebensräume in landwirtschaftliche Flächen, vor allem für den Anbau von Kartoffeln, aus.[7] Die Tiere meiden landwirtschaftliche Felder, und im größten Teil ihres Verbreitungsgebietes leben die Tiere in kleinen Bereichen, häufig entlang von Eisenbahnstrecken.[1]
Der Perote-Ziesel (Xerospermophilus perotensis, Syn.: Spermophilus perotensis) ist eine Hörnchenart aus der Gattung Xerospermophilus. Er lebt ausschließlich in einem abgegrenzten Gebiet in Zentralmexiko.
The Perote ground squirrel (Xerospermosphilus perotensis) is a species of rodent in the family Sciuridae.[2] It is endemic to Mexico and is currently at risk of extinction. Perote ground squirrels live within the same area as rock squirrels (Otospermophilus variegatus) but they use different microhabitats. In one case it also shares its habitat with the Mexican ground squirrel (Ictidomys mexicanus).[3] Perote ground squirrels have traits similar to those of spotted ground squirrels (X. spilosoma pallescens) found in the northern Mexican Plateau; however they are larger, have shorter tails and yellow backs. Its skull is relatively narrow with a large braincase and they have heavy, thick teeth.[4] Perote ground squirrels have two annual cycles, an active phase (March–November) and a hibernation phase (December–February). Some overlap may occur in March and November however.[5]
X. perotensis was first described as a species in 1893. Much research is being done recently, and many scientists think it should be classified as a subspecies of X. spilosoma. "In either case, and regardless of the position one might adopt around species concepts, it is evident that X. perotensis constitutes an independent and isolated biological entity that has evolved under restricted geographical and ecological contexts as a consequence of recent Pleistocene events".[5]
The Perote ground squirrel’s closest relative is believed to be the spotted ground squirrel (X. spilosoma) which split from each other 1.2-3.3 million years ago as a result of climate shifts during the Pleistocene.[6]
The habitat range of the Perote ground squirrel is in the Oriental Basin (5250 km2) between Puebla and Veracruz. The basin is surrounded by high mountains [6] thought to have arisen from volcanic activity. This also accounts for the pockets of arid and semiarid land.[4] The semiarid land in Perote is the most humid in the area with an average rainfall of 369.77 mm between June and September. The average temperature is 11.9 °C with highs of 14.73 °C and lows of 8.80 °C.[3]
Perote ground squirrels only live in alkaline grasslands, arid scrubs and hilly, rocky areas where they will dig their burrows. However, due to agriculture, overgrazing, and the urbanizing of the area, the suitable habitat for the squirrel is down to 16 small localities. These areas are mostly narrow strips (20–50 m) separated by an average distance of 15.8 km.[6]
This species is threatened by extensive habitat fragmentation and deforestation within its restricted range due to timber extraction and clearing of forest for agriculture. While the squirrel once occupied a range of approximately 5250 square kilometers, it now only occupies an area totaling 2457 square kilometers.[3] The Oriental Basin is surrounded almost entirely by a belt of temperate mountain ranges, which prevent the squirrel from dispersing to new habitat.[4] The Oriental Basin is made up of lava flows, isolated mountains, and volcanoes and so provides only localized habitable areas.
X. perotenses is a generalist species in its diet. It is mostly found in croplands and open areas with low vegetation.[5] In most studies, researchers bait traps with oats in order to catch individuals.
Perote ground squirrels form family groups within individual burrow systems. In some cases males will leave the burrow to locate females in dispersed areas. This causes aggression between adults and yearling males that ultimately leads to further male migration.[6] Adult males become active in March (before sub-adults and females). Copulation occurs between April and May and pregnant and/or lactating females were most common in June–August. The average number of embryos was found to be six, where the average number of live juveniles was four.[3]
Due to the habitat destruction and fragmentation of land, there are fewer opportunities for breeding between genetically diverse individuals. Perote ground squirrels have been seen mating within their own family, which may lead to inbreeding. However, results have shown that "no inbreeding coefficient value for any population was significantly different from zero, implying that inbreeding had little effect on genetic structure."[6]
Due to the increased fragmentation of the ground squirrels native habitat, they have suffered a sharp decrease in genetic diversity. By comparing mitochondrial DNA of current populations with historic museum specimens, scientists have observed a decrease in haplotype and nucleotide diversity.[6] Because of rapid generation times and large effective population sizes, Sciurids are expected to exhibit high numbers of haplotypes; however, the Perote Ground Squirrel is an exception to the rule. Scientists are concerned that this loss of genetic diversity may contribute to their eventual extinction. It is recommended that management action be taken to help increase genetic diversity; the most likely solution being a relocation of certain individuals within each of the 16 populations.
Species can respond to environmental change in one of three possible ways: (a) migrating; that is, tracking their ecological niche throughout the geographic space. The Perote ground squirrel has such particular environmental needs that they do not have a place to migrate. (b) adapting in terms of evolutionary change and/or physiological acclimation; and (c) becoming locally extinct." [5]
Some studies have found that because the Perote ground squirrel is a seasonal species, it is more affected by climate change, increasing the risk of extinction. Seasonal species are more vulnerable because they are forced to do all their annual activities in a shorter amount of time. They do not migrate and have to adjust their activities, such as hibernation, with the current climate.[5]
The squirrel also has predators such as the long-tailed weasel (Mustela frenata) and domestic dogs, which have impacts on population.[6]
"Ground-dwelling small mammals are key species, considered as ecosystem engineers because of their positive effects on soil condition, by introducing organic matter, favoring water infiltration and modifying its physical structure, thus enriching vegetation composition and favoring phreatic aquifer maintenance. Their burrows often provide microhabitats for other vertebrate and invertebrate species. In addition, ground squirrels are important prey for several predator species, some of which highly depend on them during their breeding season."[5] If the ground squirrel were to go extinct, there would be a dramatic change in the ecosystem.
There are many gaps in the studies of the Perote ground squirrel. Even though it is endangered, we have much to learn. Maybe further studies may provide an answer on how we can conserve this keystone species of the Oriental Basin in Mexico. Unfortunately, many experts fear the squirrel will go extinct without human intervention.
The Perote ground squirrel (Xerospermosphilus perotensis) is a species of rodent in the family Sciuridae. It is endemic to Mexico and is currently at risk of extinction. Perote ground squirrels live within the same area as rock squirrels (Otospermophilus variegatus) but they use different microhabitats. In one case it also shares its habitat with the Mexican ground squirrel (Ictidomys mexicanus). Perote ground squirrels have traits similar to those of spotted ground squirrels (X. spilosoma pallescens) found in the northern Mexican Plateau; however they are larger, have shorter tails and yellow backs. Its skull is relatively narrow with a large braincase and they have heavy, thick teeth. Perote ground squirrels have two annual cycles, an active phase (March–November) and a hibernation phase (December–February). Some overlap may occur in March and November however.
X. perotensis was first described as a species in 1893. Much research is being done recently, and many scientists think it should be classified as a subspecies of X. spilosoma. "In either case, and regardless of the position one might adopt around species concepts, it is evident that X. perotensis constitutes an independent and isolated biological entity that has evolved under restricted geographical and ecological contexts as a consequence of recent Pleistocene events".
Xerospermophilus perotensis es una especie de roedor de la familia Sciuridae.[2]
Su hábitat natural son: zonas subtropicales o tropicales áridas de tierras de gran altitud, pastizales.
Spermophilus perotensis Spermophilus generoko animalia da. Karraskarien barruko Xerinae azpifamilia eta Sciuridae familian sailkatuta dago.
Spermophilus perotensis Spermophilus generoko animalia da. Karraskarien barruko Xerinae azpifamilia eta Sciuridae familian sailkatuta dago.
페로테땅다람쥐(Xerospermophilus perotensis)는 다람쥐과에 속하는 설치류의 일종이다.[2] 멕시코의 토착종으로 현재 멸종 위기종이다. 페로테땅다람쥐는 바위다람쥐와 같은 지역에서 서식하지만 미소 서식 환경이 차이가 난다. 한 사례로 멕시코땅다람쥐와 서식지를 공유하기도 한다.[3] 페로테땅다람쥐는 멕시코 고원 북부 지역에서 발견되는 연한반점땅다람쥐(X. spilosoma pallescens)와 유사한 형질을 갖고 있다. 그러나 더 크고 짧은 꼬리와 노랑 등을 갖고 있다. 두개골은 비교적 좁으며, 머리는 크고 이빨은 굵고 두껍다.[4] 페로테땅다람쥐는 연중 2개의 생활환을 가지는 데, 하나는 3월부터 11월 사이의 활동기이고 나머지는 12월부터 2월까지의 동면기이다. 그러나 일부는 3월과 11월에 겹친다.[5] 1893년에 처음 기술되었다. 최근에 대부분의 연구가 이루어졌고, 많은 과학자들이 반점땅다람쥐의 아종으로 간주하고 있다.
다음은 2009년 헬겐(Helgen)과 2012년 페르난데스(Fernández) 등의 연구에 기초한 계통 분류이다.[6][7]
마멋족 피그미땅다람쥐속페로테땅다람쥐(Xerospermophilus perotensis)는 다람쥐과에 속하는 설치류의 일종이다. 멕시코의 토착종으로 현재 멸종 위기종이다. 페로테땅다람쥐는 바위다람쥐와 같은 지역에서 서식하지만 미소 서식 환경이 차이가 난다. 한 사례로 멕시코땅다람쥐와 서식지를 공유하기도 한다. 페로테땅다람쥐는 멕시코 고원 북부 지역에서 발견되는 연한반점땅다람쥐(X. spilosoma pallescens)와 유사한 형질을 갖고 있다. 그러나 더 크고 짧은 꼬리와 노랑 등을 갖고 있다. 두개골은 비교적 좁으며, 머리는 크고 이빨은 굵고 두껍다. 페로테땅다람쥐는 연중 2개의 생활환을 가지는 데, 하나는 3월부터 11월 사이의 활동기이고 나머지는 12월부터 2월까지의 동면기이다. 그러나 일부는 3월과 11월에 겹친다. 1893년에 처음 기술되었다. 최근에 대부분의 연구가 이루어졌고, 많은 과학자들이 반점땅다람쥐의 아종으로 간주하고 있다.
