Spermophilus saturatus

"Restricted to the Cascade Mountains of Washington State and British Columbia, Cascade golden-mantled Ground Squirrels are so similar to golden-mantled Ground Squirrels that some scientists consider them the same species. However, their ranges are separated by the Columbia River. Like other ground squirrels, they are active during the day and forage on the ground for a variety of leaves, fruits, flowers, and fungi. They are common in alpine habitat, forests, meadows, and sagebrush. Hibernation puts them into a deep energy-saving mode from fall through early spring. Each animal dens alone, its temperature dropping to only a few degrees above freezing and its metabolic rate slowing to about five percent of the summer rate. The long torpor is broken by brief periods when the squirrel's temperature comes up to normal. Cascade golden-mantled Ground Squirrels superficially resemble chipmunks, but are larger, and the white stripe along the flank stops at the shoulder rather than continuing onto the cheek as it does in chipmunks."

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occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Cascade Mountains from southern British Columbia (west to the Fraser River, north to the Nicola River, east to the Okkanagan River) south to Columbia River in Washington (Trombulak 1988; Leung and Cheng, 1992 COSEWIC report).

This species is found in the Cascade Mountains from southern British Columbia in Canada (west to the Fraser River, north to the Nicola River, east to the Okkanagan River), south to Columbia River in Washington in the United States (Trombulak 1988).

The distribution of Spermophilus saturatus lies exclusively within a limited area of the Pacific Northwest region of North America. This species is unique to the Cascade Mountains of Washington and southern British Columbia, where it occupies a narrow band between the Columbia River in the south and the Nicola River in the north. The northern extent of its range is fragmented and not well documented.

Biogeographic Regions: nearctic (Native )

Spermophilus saturatus is a handsome ground squirrel. It has a sturdy build with a chipmunk-like pelage. The head and shoulders are characterized by a poorly defined russet-colored mantle, and its eyes are bordered by a light buff colored ring. The dorsum of this species is grayish-brown with a white stripe on each side. The white stripe begins behind the shoulders and extends most of the way down the back. This white stripe is bordered on each side by two black stripes, which are sometimes poorly defined. The underside, feet, and tail are buff colored.

Spermophilus saturatus is distinguished from chipmunks (Tamius spp.) in that its dorsal stripes do not continue onto its face. Cascade golden-mantled ground squirrels are also larger than any of the chipmunks. These ground suirrels measure from 287 to 315 mm. Weigh varies seasonally, between 200 g at emergence from hibernation in the spring and 300 g, a whopping weight reached when fat reserves are at their pre-hibernation maximum. There is no significant sexual dimorphism.

Of the three species in the subgenus Calospermophilus, S. saturatus is the largest. Spermophilus lateralis, its closest relative, is smaller and has a more developed mantle. The other, Spermophilus madrensis, is much smaller and almost completely lacks the mantle of the others.

Range mass: 200 to 350 g.

Range length: 287 to 315 mm.

Average length: 305 mm.

Sexual Dimorphism: sexes alike

Average basal metabolic rate: 0.849 W.

Weight: 300 grams

Sexual Dimorphism: None

Length:
Average: 302 mm
Range: 286-315 mm

Weight:
Range: 200-300 g

Comments: Talus slides and clearings; krummholz; closed coniferous forest, pine woodland, and adjacent open meadows and sagebrush steppe Trombulak, in Wilson and Ruff 1999). In underground burrow when inactive (Trombulak 1988). Young are born in underground burrows.

Habitat and Ecology

Systems

• Terrestrial

Spermophilus saturatus occupies alpine habitat most often within the transition zone on the drier eastern side of the Cascade Mountain range. It is uncommon on the damper west side of the range. This species occurs in alpine talus, meadows, and in mixed coniferous forests. It prefers habitat that provides plenty of cover, with brush, logs, and trees. Spermophilus saturatus is often found in the open yellow pine (Pinus ponderosa) stands of the eastern Cascades among sagebrush and grassland, but rarely away from the cover of logs and trees.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: forest ; scrub forest ; mountains

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Comments: Eats fungi (especially in fall), green vegetation, seeds, small fruits, carrion. In one study (Trombulak 1987), diet primarily VICIA leaves and fungi. Generally forages on ground, may climb into bushes and conifers.

Spermophilus saturatus is primarily a mycovore and herbivore. Individual diet is variable, and depends on the specific habitat in which an animal resides. One study showed that in meadows, the diet consisted of 44% hypogeous fungi, 21% vetch leaves, 10% bark, 6% grasses, and 1% conifer seeds. In forested habitat, the diet was 63% hypogeous fungi with a proportionately smaller amount of plant material.

Spermophilus saturatus often forages on the ground for pine cones that have been dropped by Douglas squirrels Tamiasciurus douglasii.

Other items found in the diet of S. saturatus include: dandelion flowers, tubers, lupine seeds, and the berries of salal, huckleberry, and mountain ash.

Finally, this species has been known to forage on road-kill, even that of conspecifics.

Animal Foods: carrion

Plant Foods: leaves; roots and tubers; wood, bark, or stems; seeds, grains, and nuts; fruit; flowers

Other Foods: fungus

Primary Diet: herbivore (Folivore ); mycophage

Spermophilus saturatus is a primary consumer, converting plant energy into body mass, and therefore making it available to upper level consumers. As listed above it is a prey species for many raptors and carnivores.

As a seed and fungus eater, S. saturatus decreases plant and fungus regeneration but is also likely responsible for dispersing seeds and spores throughout its range.

The digging of this species can facilitate soil mixing and aeration, and abandoned burrows can become home to other underground nesting animals.

Spermophilus saturatus has an interesting relationship with other rodents that live in close proximity to it. It often lives near and tolerates yellow-pine chipmunks, Tamius amoenus. They seems to avoid aggressive interactions by occupying different feeding niches. T. amoenus eats more plant seeds, whereas S. saturatus eats more leaves and stems. The two species have been known to forage non-aggressively within 5 cm of each other, and nest within 10 meters of each other. They also live in close proximity to Douglas squirrels, Tamiasciurus douglasii. T. douglasii generally climbs pine trees for cones and seeds, whereas S. saturatus forages for pine seeds on cones that have dropped - often by Douglas squirrels.

Ecosystem Impact: disperses seeds; creates habitat; soil aeration

Commensal/Parasitic Species:

• Rocky Mountain spotted fever

Spermophilus saturatus is a prey species for many raptors and carnivores. Anti-predator behaviors include scanning for predators from prominent logs or stumps, then diving for cover at the first sign of danger. Burrows often have multiple entrances to escape digging predators and so they have more access to safety from above.

Female ground squirrels keep a close eye on offspring for a time after they first exit the natal burrow and will assist juveniles back into the burrow if danger has been spotted.

Alarm calls likely warn other individuals and kin if predators are approaching. This species is known to respond to the alarm calls of Marmota flaviventris.

Known Predators:

• Northern goshawks (Accipiter gentilis)
• red-tailed hawks (Buteo jamaicensis)
• great horned owls (Bubo virginianus)
• merlins (Falco columbarius)
• long-eared owls (Asio otus)
• coyotes (Canis latrans)
• red foxes (Vulpes vulpes)
• long-tailed weasels (Mustela frenata)
• American martens (Martes americana)
• bobcats (Lynx rufus)

May live in colonies, but population densities typically are low (3/ha in forest, 5-12/ha in adjacent meadow in Washington). Populations may be highest in parks where human refuse is available as food. Relatively mobile; large % of residents may be immigrants (Trombulak 1987). Sedentary in British Columbia. EUTAMIAS AMOENUS occurs sympatrically.

Spermophilus saturatus has both a very good sense of sight, and hearing. It perceives danger primarily by spotting approaching predators. Individuals often scan for predators from a prominent perch on a stump or log. Given their good vision, it is likely that members of this species use some visual means of communication, such as body postures. Individuals often give an alarm call as they dive into their burrows.

Very little is documented about the methods of communication between individuals of S. saturatus. Banfield wrote about the communication of Spermophilus lateralis, which he considers to be the same species. He describes three calls: a high-pitched two-noted whistle, an explosive alarm call, and a buzzing chatter that individuals make when they are cornered.

Another study describes the relationship between S. lateralis and yellow-bellied marmots Marmota flaviventris . Each species responds to the alarm calls of the other, and will take appropriate cover upon hearing such calls. These squirrels distinguish alarm calls from other loud noises, and will seek refuge at the sound of an alarm call from the other species even though the animals of the two species do not normally interact.

Although not specifically mentioned in the literature, it is reasonable to assume that these animals use some forms of tactile communication. Mothers communicate with their young through touching, as do mates. Males may have some tactile communication with one another while defending their territories.

Communication Channels: visual ; tactile ; acoustic

Perception Channels: visual ; acoustic

Comments: Emergence from hibernation varies among years from mid-April to mid-May; yearlings emerge 1-2 weeks later than adults. Adults and yearlings end activity mid-August to late September; juveniles active into November and early December (Trombulak 1988).

Individuals of S. saturatus are known to have lived at least 4 years in the wild. Their average lifespan is not known, nor is their maximum possible lifespan.

Range lifespan
Status: wild: 4 (high) years.

Observations: In the wild, these animals have lived at least 4 years, but their maximum longevity is probably much longer. They are sexually mature after they emerge from their first hibernation (Trombulak 1988).

Copulation occurs in late April-early May. Gestation lasts 28 days. Litter size is 1-5 (average 4); one litter/year (Trombulak 1988). Females may breed as yearlings, males usually not until second year. Juveniles emerge from natal burrows in July-early August (Trombulak 1987).

Cascade golden-mantled ground squirrels are polygynous. Males emerge earlier from hibernation and then guard a territory waiting for the females to emerge and begin estrous. Males will mate with females who reside within theor territory.

Somewhat atypically, in the fall males usually enter into hibernation later than females. This is thought to be a mating strategy. In other species of ground-dwelling sciurids, males typically enter into hibernation before females, because, lacking the high energy demands of lactation, they are able to achieve adequate fat reserves early, and are less prone to heat stresses if they begin hiberation soon. In species where males enter hibernation after females, it is generally because it takes males longer than it does females to store enough food winter snacking. Spermophilus saturatus is not known to store food. It is thought that the reason for the later immergence of males is that it allows them to see where the females are hibernating, then following spring they remember where the females will be emerging when they are ready to mate.

Mating System: polygynous

Reproduction in this species is timed to coincide with emergence from hibernation. In the early spring (early April to late May), adult males emerge from hibernation. They defend territories and wait for females to emerge. Adult females emerge less than 15 days after males. Mating begins a few days after the females emerge and lasts up to two weeks. The mating season is highly synchronous, and females will birth one litter/year.

Gestation lasts only 28 days, after which the female gives birth to as many as five pups. Juveniles weigh only 6 grams and are highly altricial at birth. They develop rapidly, and first appear from the burrow about 36 days after birth. Usually three pups survive to emergence, at which point they weigh around 85 grams.

Juveniles are weaned at least one week after they emerge. For a short time after their first emergence, the mother keeps a close eye on the young and will help them back into the burrow if there is any sign of danger. However, usually by mid-July they are on their own to leave the burrow. Both sexes disperse from their natal burrow and establish their own home range. They have been found to disperse up to 300 meters from the natal burrow.

Juveniles reach adult size and sexual maturity the following spring, which is slightly less than a year after they are born. Although sexually mature, yearling females and males reproduce at lower rates than do full adults. Reproduction for adult females and males is nearly 100%, whereas it varies from 50 to 100% for yearling females. Only about 10% of yearling males breed.

Breeding interval: Cascade golden-mantled ground squirrels breed once yearly.

Breeding season: Breeding occurs from April to May.

Range number of offspring: 3 to 5.

Average gestation period: 28 days.

Average weaning age: 6 weeks.

Average time to independence: 2 months.

Average age at sexual or reproductive maturity (female): 10 months.

Average age at sexual or reproductive maturity (male): 10 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average birth mass: 5.97 g.

Average gestation period: 28 days.

Average number of offspring: 4.16.

Average age at sexual or reproductive maturity (male)
Sex: male: 335 days.

Average age at sexual or reproductive maturity (female)
Sex: female: 335 days.

Males are not involved in the parental care of this species. Females give extensive parental care to their altricial young until they are weaned. She provides the young with milk, grooming, and protection. After the young emerge from the burrow, the mother keeps a close eye on them for protection and warning, until it is time for them to disperse.

Parental Investment: no parental involvement; altricial ; female parental care ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G5 - Secure

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 1996
  Lower Risk/least concern
  (Baillie and Groombridge 1996)

Spermophilus saturatus is fairly common where it occurs. Due its limited range and relative rarity there has been some interest in determining its overall status. This is the case in British Columbia, where the ground squirrel is only found in a small portion of the province. In 1998, this species was on the provincial blue list for species that are vulnerable or sensitive. A 1999 report found that it appears to not be at risk though further information is required to determine its overall status. Not much is confidently known about its population trends and threats. It is still on the provincial blue list. Some potential threats could be timber harvesting, road construction, and competition with other rodents, specifically the Columbian ground squirrel Spermophilus columbianus.

Spermophilus saturatus occurs in several protected areas throughout its range. These include Manning Provincial Park, and Cathedral Provincial Park in British Columbia and North Cascades National Park and Mount St. Helens National Volcanic Monument in Washington.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Population

Population Trend

Comments: No significant threats; see 1992 COSEWIC report by Leung and Cheng.

Major Threats

Conservation Actions

The lifestyles of ground squirrels are often in conflict with human economic interests because of their food choices and digging habits. Much research, expense, and effort has been put forth to control ground squirrel populations. Spermophilus saturatus is fortunate because its limited range most often keeps it away from human economic interests. It seldom inhabits agricultural areas, where most conflicts occur. One potential conflict may be with the timber industry which has extensive tree plantations within the range of S. saturatus. This species eats conifer seeds and can damage planted seedlings. However, the actual cost to the timber industry is likely negligible. Futhermore, this damage is likely countered by the number of seeds and spores these animals disperse.

Finally, being an intermediate host to Rocky Mountain spotted fever can cause concern because of its potential transmission to humans by infected ticks.

Negative Impacts: injures humans (carries human disease); crop pest

Spermophilus saturatus has little economic importance to humans. Its limited distribution reduces human contact, though it often provides much entertainment to campers and hikers who venture into its habitat.

Positive Impacts: research and education