These animals are eaten primarily by diurnal, desert-dwelling predators, some of which are listed here.
They animals tend to run away from predators instead of seeking shelter. When they are running away, they very seldom look back. This species has slightly longer feet than other antelope squirrel species, which enable them to run faster. They can also escape into their burrow if there is an opening nearby. (Johnson and Harris, 2001; Belk and Smith, 1991)
Known Predators:
Ammospermophilus leucurus appear quite similar to other antelope ground squirrels. They have slightly longer legs and small, rounded ears. White-tailed antelope squirrels are whitish on their ventral surface. Their backs are brown to gray in color with two white stripes from the shoulder to the hind end. The outer surfaces of all legs are somewhat more reddish in color. The underside of their tails are pure white and they have a subterminal black band on the tail.
They range in total length from 188 to 239 mm and in tail length from 42 to 87 mm. They weigh from 96 to 117 grams.
The hair of the tail molts in the fall and the rest of the hair molts once in spring and then again in fall. White-tailed antelope squirrels have cheek pouches that they can carry food in. They also have ten mammae, slightly more than other ground squirrels, which typically have four to seven.
(Nowak, 1999; Belk and Smith, 1991; Tomich, 1982)
Range mass: 96 to 117 g.
Average mass: 105 g.
Range length: 188 to 239 mm.
Average length: 211 mm.
Other Physical Features: endothermic ; bilateral symmetry
Average basal metabolic rate: 0.511 W.
There are nine subspecies of A. leucurus in the United States.
(Tomich, 1982)
Perception Channels: tactile ; chemical
These animals are abundant in suitable habitat throughout their range.
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
White-tailed antelope squirrels can become bothersome to farmers. This rarely happens because A. leucurus lives in deserts where there are very few farms. However, in some areas they occasionally cause trouble by burrowing on farmland and eating crops.
(Nowak, 1999)
Negative Impacts: crop pest
White-tailed antelope squirrels make good research subjects because they can be easily studied.
(Nowak, 1999)
Positive Impacts: research and education
White-tailed antelope squirrels store seeds in food caches, possibly resulting in the dispersal and germination of seeds.
(Belk and Smith, 1991)
Ecosystem Impact: disperses seeds
During the year, different food sources make up the bulk of the diet. During the spring, greens are widely available, so they consitute the bulk of the diet, or approximately 60%. In the fall, when greens are not readily available, they only comprise about 20% of the diet. Seeds and fruits are the most important food source in the fall, making up about 60% of the diet, and are not as important in the spring, making up about 20% of the diet. Invertebrates, mainly insects, make up the rest of their diet during the year. Compared to other antelope squirrels, A. leucurus was found to be more carnivorous. The use of efficient kidneys keeps water loss low, but they must have some succulent plants or free water in their diet in order to survive. Foraging by A. leucurus occurs in trees and shrubs or on the ground. White-tailed antelope squirrels have cheek pouches in which they can store food until they return to their burrows, where they will hoard the food, or put it into a cache, as do other squirrels.
Common foods eaten include: seeds, green vegetation, including grasses, mesquite, acacia, yucca, ephedra Mormon tea, Joshua tree, evening primrose, storksbill, blackbrush and opuntia cactus, fruits, invertebrates, carrion.
(Johnson and Harris, 2001; Belk and Smith, 1991; Tomich, 1982)
Animal Foods: carrion ; insects
Plant Foods: leaves; seeds, grains, and nuts; fruit
Foraging Behavior: stores or caches food
Primary Diet: omnivore
White-tailed antelope squirrels are found in northwestern New Mexico, western Colorado, southeastern Oregon, northern Arizona, southwestern Idaho, Utah, southern Nevada, southern California, and as far south as the southern Baja California peninsula. Of all Ammospermophilus, white-tailed antelope squirrels are the most widespread in North America; their general range is the Great Basin to Baja California.
(Belk and Smith, 1991; Tomich, 1982)
Biogeographic Regions: nearctic (Native )
White-tailed antelope squirrels live in deserts and foothills. These areas are sandy, gravelly or rocky, provided the soil can be burrowed in to escape from extreme heat and predators. Ammospermophilus leucurus will use burrows of other rodents, such as kangaroo rats, for shelter and will make numerous burrows of its own within its home range. Common habitats include desert succulent shrub, riparian, and wash areas. Ammospermophilus leucurus also occurs in chaparral and grassland.
(Johnson and Harris, 2001; Belk and Smith, 1991)
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: desert or dune ; chaparral
Average lifespan is not known, but one white-tailed antelope squirrel lived five years and ten months in captivity. The average lifespan for other members of this genus is typically one year.
(Nowak, 1999)
Average lifespan
Status: captivity: 5.8 years.
Males and females are sexually mature by the end of their first year. The breeding season for A. leucurus is in spring, between February and June. Usually females have one litter per year with between five and fourteen babies per litter. Litter size seems to depend on the quantity of green vegetation available to the mother. The young weigh about three or four grams at birth. Sometimes a female will have two litters in one year. Gestation time is probably between thirty and thirty-five days.
(Johnson and Harris, 2001; Nowak, 1999; Belk and Smith, 1991)
Breeding season: February through June
Range number of offspring: 5 to 14.
Average number of offspring: 8 or 9.
Range gestation period: 30 to 35 days.
Range weaning age: 65 (low) days.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
Average birth mass: 3.21 g.
Average number of offspring: 8.
Average age at sexual or reproductive maturity (male)
Sex: male: 365 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 365 days.
Ammospermophilus leucurus build nests for the young near the center of the burrow. Nests are made from dry plant materials and animal fur. When the young are born, they are helpless and without adult fur; their eyes and ears are closed. Young come out of the burrow about one or two weeks before weaning, at approximately 2 months of age.
(Johnson and Harris, 2001; Belk and Smith, 1991)
Parental Investment: altricial ; female parental care
Ammospermophilus leucurus[1] a zo ur spesad bronneged krigner eus kerentiad ar Sciuridae.
Bevañ a ra diwar deil (10-60%), had (20-50%), artropoded ha mellkeineged (glazarded ha krignerien dreist-holl).
Al loen a vev an nav isspesad anezhañ[2] :
e mervent Norzhamerika ha ledenez Baja California.
a vo kavet e Wikimedia Commons.
Der Weißschwanz-Antilopenziesel (Ammospermophilus leucurus) gehören zur Gattung der Antilopenziesel. Er kommt in Teilen der westlichen Vereinigten Staaten sowie in Mexiko (Baja California) vor.
Weißschwanz-Antilopenziesel haben eine Länge von 18 bis 23 cm und ein Gewicht von 100 bis 140 g. Die Art ist braun gefärbt und hat einen weißen Schwanz. Sie leben in Wüsten, Halbwüsten und auf sandigen Ebenen mit wenig Grasbewuchs, wo sie gut graben können, um der Hitze und den Fressfeinden (u. a. Füchse, Luchse, Greifvögel, Klapperschlangen) zu entgehen.
Die Tiere kommen in den Vereinigten Staaten vom Süden von Oregon und dem Osten Kaliforniens bis Colorado, Utah, Nevada, New-Mexico und Arizona sowie auf der mexikanischen Halbinsel Baja California vor.[1]
Ziesel fressen Samen, Früchte und Wurzeln und gegebenenfalls auch Insekten. Die Nahrung wird in den Backentaschen verstaut.
Der Weißschwanz-Antilopenziesel wird als eigenständige Art innerhalb der Gattung der Antilopenziesel (Ammospermophilus) eingeordnet, die aus fünf Arten besteht.[2][3] Die wissenschaftliche Erstbeschreibung als Spermophilus harrisii stammt von Clinton Hart Merriam aus dem Jahr 1889 anhand von Individuen vom San-Gorgonio-Pass, Riverside County, in Kalifornien.[2][4] Er beschrieb die Art als Tamias leucurus in Abgrenzung zum Harris-Antilopenziesel (Ammospermophilus harrisii, damals Tamias harrisii) und ordnete sie damit den Streifenhörnchen (Gattung Tamias). Babei benutzte er bereits den Namen antelope squirrel und stellte die Zuordnung zu Tamias in Frage.[5] 1907 wurde die Art durch Edgar Alexander Mearns in die bereits 1862 von Clinton Hart Merriam eingerichtete Gattung Ammospermophilus überstellt.[4]
Innerhalb der Art werden mit der Nominatform neun Unterarten unterschieden:[3]
Der Weißschwanz-Antilopenziesel wird von der International Union for Conservation of Nature and Natural Resources (IUCN) als nicht gefährdet (least concern) eingestuft. Begründet wird dies durch das vergleichbar große Verbreitungsgebiet, die angenommen großen Bestandszahlen und die relativ geringen Rückgänge der Populationen.[1] Die Bestandsdichte in den Vereinigten Staaten ist gering und liegt bei 0,06 pro Hektar im Frühjahr bis 0,35 pro Hektar im Herbst, wobei die Bestandszahlen jährlich stark fluktuieren können.[1] Bestandsgefährdende Risiken für die Art sind nicht bekannt, allerdings sind sie auf einigen Inseln im Golf von Kalifornien durch verwilderte Hauskatzen bedroht.[1]
Der Weißschwanz-Antilopenziesel (Ammospermophilus leucurus) gehören zur Gattung der Antilopenziesel. Er kommt in Teilen der westlichen Vereinigten Staaten sowie in Mexiko (Baja California) vor.
The white-tailed antelope squirrel (Ammospermophilus leucurus) is a diurnal species of ground squirrel, scientifically classified in the order Rodentia and family Sciuridae, found in arid regions of the southwestern United States and the Baja California Peninsula of northwestern Mexico.
The white-tailed antelope squirrel's geographical range extends north to south from southwestern Oregon to New Mexico, and east to west from western Colorado to Baja California, Mexico.[2][3][4]
This species of squirrel has an average home range of 14.9 acres (60,000 m2), and utilizes approximately 4 acres (16,000 m2) in its daily activities.[5] Throughout much of the squirrel's range, especially in Utah, the population density fluctuates greatly, with periods of high density followed by periods of low density.[2][6] Average population density also varies by season, with higher density in autumn relative to late spring.[2][7]
The white-tailed antelope squirrel is commonly spotted in arid habitats throughout the southwestern United States.[2] Throughout this range, Ammospermophilus leucurus is omnivorous, feeding primarily on foliage (10%-60% of its diet), seeds (20%-50%), arthropods, and to a lesser extent, vertebrates (mainly lizards and rodents; predatory behavior by ground squirrels has been noted[8][9][10][11]).[12] In conjunction with being a predator, the white-tailed antelope squirrel is also prey to many larger animals, including raptors, various canids, and snakes.[2][3][4][6] These squirrels are not only preyed upon by large predators, but they also fall victim to many diverse ectoparasites. These include various ticks, fleas, mites, lice, and a couple species of parasitic larvae.[2]
Antelope squirrels are active most during the cooler parts of the daylight hours, avoiding midday as much as possible.[2][13] Although these animals live in hot and arid climates, the white-tailed antelope squirrel is diurnal, meaning heat gain from metabolic activity could be a problem. However, compared to direct exposure of heat from the sun, metabolic heat gain contributes little to the overheating of this species.[2][13] This diurnal activity pattern may be contributed to predation patterns.[14] Selective pressures may have led to this species avoiding nighttime activity due to increased predation by nighttime predators. This behavior is controlled by the squirrels' natural circadian rhythms, and research has shown these rhythms to be highly important in keeping these diurnal activity patterns intact.[14]
White-tailed antelope squirrels' reproductive receptiveness in females and reproductive capability in males peaks in early spring.[15] It only takes the squirrels one year to become sexually mature and begin reproducing; typically, antelope ground squirrels will produce one large litter per year.[15]
Geographical factors, and thus environmental factors, weigh heavily on Ammospermophilus leucurus' reproductive cycle length and average litter size.[16] Specifically, this variation is seen best when comparing the northern and southern extents of the antelope ground squirrels' distribution. In Oregon, which is the northernmost extent of the squirrels' range, reproductive cycles are relatively short, and the average litter size is 9.3. However, in Baja California, the southernmost extent of the squirrels' range, reproductive cycles last half of the year, and the average litter size is 5.9.[16]
{{cite web}}: CS1 maint: archived copy as title (link) The white-tailed antelope squirrel (Ammospermophilus leucurus) is a diurnal species of ground squirrel, scientifically classified in the order Rodentia and family Sciuridae, found in arid regions of the southwestern United States and the Baja California Peninsula of northwestern Mexico.
Ammospermophilus leucurus Ammospermophilus generoko animalia da. Karraskarien barruko Xerinae azpifamilia eta Sciuridae familian sailkatuta dago.
Ammospermophilus leucurus Ammospermophilus generoko animalia da. Karraskarien barruko Xerinae azpifamilia eta Sciuridae familian sailkatuta dago.
Ammospermophilus leucurus est un rongeur de la famille des Sciuridae. Il vit aux États-Unis et au Mexique.
Selon MSW :
Ammospermophilus leucurus est un rongeur de la famille des Sciuridae. Il vit aux États-Unis et au Mexique.
Il citello antilope dalla coda bianca (Ammospermophilus leucurus (Merriam, 1889)) è uno scoiattolo appartenente al genere dei citelli antilope (Ammospermophilus). È diffuso in alcune parti degli Stati Uniti occidentali e in Messico (Bassa California).
I maschi di citello antilope dalla coda bianca raggiungono una lunghezza testa-tronco di circa 18,8-22,0 centimetri, ai quali si aggiungono 4,2-7,1 centimetri di coda, e un peso compreso tra 103,7 e 116,8 grammi. Le femmine, d'altro canto, raggiungono una lunghezza testa-tronco di circa 20,2-21,6 centimetri, ai quali si aggiungono 5,5-6,6 centimetri di coda, e un peso compreso tra 96,2 e 104,5 grammi.[2] Questi citelli hanno la testa e il dorso di colore variabile dal grigio al grigio ardesia, con una striscia bianca che corre lungo ogni lato del corpo. Il ventre va dal bianco al crema. Il muso e le zampe presentano delle sfumature che vanno dall'arancio chiaro al ruggine. La coda è di colore grigio brizzolato con la parte inferiore biancastra e una fascia nera nei pressi dell'estremità. È presente un anello orbitale chiaro.[2]
La specie è diffusa negli Stati Uniti dall'Oregon meridionale e dalla California orientale al Colorado, allo Utah, al Nevada, al Nuovo Messico e all'Arizona, nonché nella penisola messicana della Bassa California.[1]
Questo citello è diurno e attivo tutto l'anno: non va in estivazione né immagazzina riserve di grasso, nonostante le temperature torride delle aree desertiche in cui vive. Tuttavia, a differenza di altre specie proprie di questi ambienti, necessita di bere acqua per sopravvivere. Affronta il problema della termoregolazione riducendo le attività nelle ore più calde della giornata; inoltre, la sua coda, ricoperta da peli radi, sembra essere particolarmente utile per dissipare il calore. Il citello antilope dalla coda bianca vive in tane poco profonde (meno di un metro di profondità) sparse attraverso un home range di 3-8 ettari, che vengono utilizzate sia per trovare rifugio dai predatori che per evitare il calore. La tana ospita anche una camera nido rivestita con materiali morbidi.[2]
Quasi tutti gli esemplari adulti di più di un anno di età si riproducono una volta all'anno, tra febbraio e giugno nella parte settentrionale dell'areale e tra marzo e settembre in quella meridionale; generalmente la femmina dà alla luce una sola nidiata di 5-14 piccoli (mediamente 8) dopo una gestazione di 30-35 giorni. Il numero dei componenti della nidiata segue un gradiente latitudinale: presso le popolazioni settentrionali dell'Oregon la media dei piccoli è di 9,3, mentre presso quelle meridionali della Bassa California è di 5,8. I giovani emergono dalla tana a 50-60 giorni e vengono svezzati poco dopo. Successivamente, si disperdono lontano dalla loro area natale. Gli adulti conducono un'esistenza solitaria, con gerarchie di dominanza ben stabilite tra vicini di tana. Annusarsi e strofinarsi il muso a vicenda sembra essere la maniera principale per mantenere una rigida gerarchia di dominanza tra vicini. Le aggressioni possono portare a inseguimenti, battiti di denti e a veri e propri scontri fisici.[2] I citelli antilope dalla coda bianca si nutrono soprattutto di vegetazione verde, cactus, yucca e semi vari, ma possono mangiare anche insetti o carogne di vertebrati.[2]
I citelli antilope dalla coda bianca, tra i pochi roditori diurni del deserto, sembrano limitare al minimo le interazioni con i rappresentanti delle altre specie. Le densità di popolazione sono piuttosto basse, ma grazie alle loro dimensioni, relativamente «considerevoli» se paragonate a quelle di altri roditori, costituiscono la maggior parte della biomassa di roditori in molti ecosistemi di deserto. Quando sono allarmati emettono due tipi di richiami: degli striduli e rapidi cinguettii e degli acuti trilli, particolarmente ben udibili in ambiente aperto. Tra i loro predatori figurano volpi, coyote, procionidi, piccoli felidi, rapaci e serpenti.[2]
Il citello antilope dalla coda bianca viene classificato come specie indipendente all'interno del genere Ammospermophilus, che comprende quattro specie.[3][2] La prima descrizione scientifica come Spermophilus harrisii venne effettuata nel 1889 da Clinton Hart Merriam sulla base di individui provenienti dal passo di San Gorgonio, nella contea di Riverside, in California.[3][4] Successivamente descrisse la specie come Tamias leucurus per differenziarla dal citello antilope di Harris (Ammospermophilus harrisii, allora Tamias harrisii) e la classificò tra i chipmunk (genere Tamias). Essa era già nota con il nome di citello antilope e lo stesso Merriam ne mise in dubbio l'appartenenza al genere Tamias.[5] Nel 1907 la specie venne trasferita da Edgar Alexander Mearns nel genere Ammospermophilus, istituito da Merriam nel 1862.[4]
Ne vengono riconosciute in tutto dieci sottospecie:[2]
Il citello antilope dalla coda bianca viene classificato dall'Unione internazionale per la conservazione della natura (IUCN) come «specie a rischio minimo» (Least Concern). Tale status trae giustificazione dall'areale relativamente ampio, dalla presunta grande entità degli effettivi e dal declino relativamente basso delle popolazioni.[1] La densità di popolazione negli Stati Uniti è bassa, da 0,06 esemplari all'ettaro in primavera a 0,35 in autunno, con effettivi che variano notevolmente di anno in anno.[1] Non sono note minacce all'esistenza della specie, ma gli esemplari presenti su alcune isole del golfo di California sono minacciati dai gatti rinselvatichiti.[1]
Il citello antilope dalla coda bianca (Ammospermophilus leucurus (Merriam, 1889)) è uno scoiattolo appartenente al genere dei citelli antilope (Ammospermophilus). È diffuso in alcune parti degli Stati Uniti occidentali e in Messico (Bassa California).
흰꼬리영양다람쥐(Ammospermophilus leucurus)는 다람쥐과에 속하는 설치류의 일종이다.[2] 미국 남서부와 멕시코 북서부 바하칼리포르니아 반도의 건조 지역에서 발견된다.
흰꼬리영양다람쥐는 북쪽의 미국 오레곤 주 남서부 지역부터 남쪽의 뉴멕시코 지역까지, 동쪽의 콜로라도주 서부 지역부터 서쪽의 바하칼리포르니아 반도까지 분포한다. 평균 60,000m2 행동권 영역에서 살며, 하루 평균 약 16,000m2 영역 안에서 활동한다.
다음은 2009년 헬겐(Helgen) 등의 연구에 기초한 계통 분류이다.[3]
마멋족 영양다람쥐속칼리포니아 죠수아 트리 공원의 흰꼬리영양다람쥐
당근을 훔치는 새끼 흰꼬리영양다람쥐
