Sciurid Rodents Research Articles

Cooperative Breeding in Marmots

Whenever individuals live in stable social groups and not all individuals breed, group members may breed cooperatively. While well-documented in a variety of birds and mammals, there is some controversy over whether, and to what degree, sciurid rodents breed cooperatively. We identify cooperative breeding when: individuals delay dispersal beyond reproductive maturity, reproduction in mature individuals is suppressed, and when non-breeders provide alloparental care. In this paper we note that the 14 species of marmots (Marmota spp.), large ground-dwelling sciurid rodents found throughout the Northern Hemisphere, provide an excellent taxon in which to study the evolution of cooperative breeding. Marmot species fit none, some, or all of the attributes of cooperative breeding. Most interestingly, delayed dispersal and alloparental care may be de-coupled interspecifically, and possibly intraspecifically, making marmots an excellent taxon for additional study. Environmental harshness increases maturation time and is associated with dispersal delayed beyond reproductive maturity. The opportunity to gain direct fitness may be associated with gaining indirect fitness by alloparental behavior. In addition to its theoretical attraction, cooperative breeding has profound implications for conservation and management of species that breed cooperatively. To maximize marmot production, managers and breeders need to pay particular attention to social group structure to prevent the expression of reproductive suppression. If cooperative breeding results from an environmental constraint, habitat modifications may increase the percent of females that breed.

Vigilance as a benefit of intermittent locomotion in small mammals

In many animal species, locomotion is frequently interrupted by brief pauses. This intermittent locomotion is usually considered a mode of prey search, but other possible functions include reduced detection or attack by predators and improved endurance. We tested the hypothesis that pauses also serve to improve vigilance for predators in two species of sciurid rodent. Videotaping animals travelling between food-collecting and food-hoarding sites revealed that numerous short pauses comprise 5–38% of the time spent ‘moving’ in grey squirrels,Sciurus carolinensis, and 0–41% in eastern chipmunks,Tamias striatus. In this situation, search for food items did not occur, and pausing did not reduce the total time spent as a moving stimulus for predators. It also appeared that speed while running was too slow and the pauses too brief to provide an endurance advantage. As predicted by the vigilance hypothesis, both species spent more time pausing when moving away from forest cover (presumably towards areas of higher risk) than when travelling back towards forest cover. In control trials within forest cover, squirrels did not differ in time pausing when approaching and leaving patches, but chipmunks paused more when approaching patches than when leaving them. We conclude that one function of pausing in squirrels is to improve anti-predator vigilance. The occurrence of pausing by chipmunks did not match a priori predictions of the vigilance hypothesis. Because it also failed to match predictions of previous alternative hypotheses, we suggest that studies are needed to examine whether the risk of attacks by conspecifics and predators is higher for chipmunks approaching than leaving food patches in forest habitat.

Effects of vegetative variation on weaning success, overwinter survival, and social group density in golden marmots (Marmota caudata aurea)

We studied the effects of food resources on weaning success, overwinter survival, and social group density in golden marmots (Marmota caudata aurea), an Old World sciurid rodent. End‐of‐season standing crop, a measure of seasonal productivity, varied between marmot groups but seemed repeatable between years. We adjusted some of our measurements of potential food availability by marmot preferences because faecal analysis suggested that marmots foraged selectively. Some, but not all, measured fitness parameters were associated with variation in food availability. The probability of weaning young was associated with overall food availability the previous year, and there was a significant positive relationship between the early‐season food resources and the proportion of years in which a group reproduced. Weaning date, a correlate of subsequent juvenile overwinter survival, was associated with overall food availability in the same year. Non‐juvenile overwinter survival was weakly associated with food availability. Finally, marmot density was not associated with the availability of food resources. We suggest that obligate social behaviour may limit the degree to which demographic factors can track environmental variation.

Does Sociality Drive The Evolution Of Communicative Complexity? A Comparative Test With Ground‐Dwelling Sciurid Alarm Calls

While sociality has been hypothesized to drive the evolution of communicative complexity, the relationship remains to be formally tested. We derive a continuous measure of social complexity from demographic data and use this variable to explain variation in alarm repertoire size in ground-dwelling sciurid rodents (marmots, Marmota spp.; prairie dogs, Cynomys spp.; and ground squirrels, Spermophilus spp.). About 40% of the variation in alarm call repertoire size was explained by social complexity in the raw data set. To determine the degree to which this relationship may have been influenced by historical relationships between species, we used five different phylogenetic hypotheses to calculate phylogenetically independent contrasts. Less variation was significantly explained in contrast-based analyses, but a general positive relationship remained. Social complexity explained more variation in alarm call repertoire size in marmots, while sociality explained no variation in repertoire size in prairie dogs and no variation in phylogenetically based analyses of squirrels. In most cases, substantial variation remained unexplained by social complexity. We acknowledge that factors other than social complexity, per se, may contribute to the evolution of alarm call repertoire size in sciurid rodents, and we discuss alternative hypotheses. Our measure of social complexity could be used by other researchers to test explicit evolutionary hypotheses that involve social complexity.

Fungus eating by the African tortoise Kinixys spekii

Fungi are important food for many invertebrates (Moore 1996). They are also widely consumed by small mammals (Fogel & Trappe 1978, Meserve et al. 1988), and may make up more than half of the volume of food in the stomachs of sciurid and microtid rodents in temperate forests (Maser et al. 1978). The use of fungi by vertebrates has not been investigated in the tropics, although macrofungi are common in some tropical systems, such as the miombo woodlands of southern Africa (Hogberg & Piearce 1986). The use of fungi by vertebrates other than small mammals is also little known. This paper describes a quantitative analysis of the diet and food selection of a tropical tortoise reported to feed on fungi. Most terrestrial tortoises (Testudinidae) have a 'predominantly or exclusively herbivorous diet' (Pritchard 1979:247), and feed almost entirely on vascular plants (Hansen et al. 1976, Milton 1992, Rall & Fairall 1993). Nevertheless one group, namely the African hingeback tortoises Kinixys Bell, appears to be omnivorous. All species of Kinixys have been reported to eat fungi and/or invertebrates: K. erosa (Schweigger) and K. homeana Bell from West Africa (Blackwell 1968, Villiers 1958), K. lobatsiana Power and K. natalensis Hewitt from South

Temporal drop-off pattern of juvenile Ixodes pacificus (Acari: Ixodidae)

We determined the temporal drop-off pattern of juvenile western black-legged ticks, Ixodes pacificus Cooley and Kohls, by recording the time of day that replete ticks dropped off common laboratory-reared and field-caught rodents. The majority of subadult ticks dropped during daylight hours. Larvae that attached to nocturnally active murid or diurnal sciurid rodents left their hosts during slightly different periods of the day. Larvae primarily departed from murids between 14:00 and 18:00 and from sciurids between 10:00 and 14:00. Drop-off of nymphs from rodents was significantly greater between 14:00 and 18:00 than between 18:00 and 06:00, although nymphs tended to leave BALB/c white mice earlier in the day. Because subadult ticks leave diurnally or nocturnally active hosts at the same time of day, drop-off appears to be independent of the temporal patterns of host activity. Diurnal drop-off will result in engorged ticks remaining in the nests of nocturnal hosts but dropping to the ground from diurnal hosts. Thus, we propose that temporal patterns of host activity mediate the spatial distribution of I. pacificus.

Alarm calling in yellow-bellied marmots: II. The importance of direct fitness

Alarm calling in sciurid rodents is often explained by inclusive fitness benefits that callers accrue. Inclusive fitness arguments imply that indirect fitness plays an important role in the evolution and maintenance of alarm calling. A more parsimonious hypothesis is that animals alarm call to increase their direct fitness by warning their offspring. Group-living animals are related to each other social group member by a coefficient of relatedness,rthat theoretically ranges from 0–1.0. The sum of these pair-wise coefficients, ‘totalr’, reflects the magnitude of possible inclusive fitness benefits. The amount of variation in the rate of yellow-bellied marmot,Marmota flaviventrisalarm calling that was explained by direct parental care was compared with that variation explained by totalr. After pups emerged, adult females with pups called more than other age/sex classes. Additionally, 42% of the variation in the rate of calling over the entire study was a function of whether the caller was a female who had pups emerge above ground that year. Totalrexplained no significant variation in the rate of alarm calling. Alarm calling in group-living yellow-bellied marmots is a form of direct parental care and inclusive fitness, broadly defined, is of little importance for the maintenance of alarm calling.

A laboratory study of social behaviour of pairs of females during the reproductive season in Spermophilus spilosoma and Spermophilus mexicanus

Spermophilus spilosoma and Spermophilus mexicanus are closely related species with a low degree of sociality. They are sympatric in the Bolson de Mapimi (Chihuahua Desert, Mexico), where they occupy similar ecological niches. In Sciurid rodents, advanced social structures may have evolved through the formation of sedentary female groups. The purpose of this study is to compare the ability of S. spilosoma and S. mexicanus females to cohabit with another conspecific female under space constraints during the mating period. The stability of the female relationships was tested by introducing a male of the same species. In both species, females managed to cohabit under space constraints with a low level of agonism. Nevertheless, an increase of defensive behaviour and a decrease of amicable behaviour were observed during female cohabitation in S. spilosoma. Moreover, female S. mexicanus had a higher tolerance index than S. spilosoma during this same period. The introduction of a male induced an increase of the level of agonism of S. mexicanus females while no reaction was detected in S. spilosoma. These differences were discussed in terms of mechanisms which could preclude the formation of sedentary social groups of females.

Sporadic amplification of ID elements in rodents.

ID sequences are members of a short interspersed element (SINE) repetitive DNA family within the rodent genome. The copy number of individual ID elements varies by up to three orders of magnitude between species. This amplification has been highly sporadic in the order Rodentia and does not follow any phylogenetic trend. Using library screening and dot-blot analysis, we estimate there are 25,000 copies of ID elements in the deer mouse, 1,500 copies in the gerbil (both cricetid rodents), and 60,000 copies of either ID or ID-like elements in a sciurid rodent (squirrel). By dot-blot analysis, we estimate there are 150,000, 4,000, 1,000, and 200 copies of ID elements in the rat, mouse, hamster, and guinea pig, respectively (which is consistent with previous reports) and 200 copies in the hystricognath rodent, nutria. Therefore, a rapid amplification took place not only after the divergence of rat and mouse but also following the deer mouse (Peromyscus) and hamster split, with no evidence of increased amplifications in hystricognath rodents. No notable variations of sequences from the BC1 genes of several myomorphic rodents were observed that would possibly explain the varied levels of ID amplification. We did observe subgenera and species-group-specific variation in the ID core sequence of the BC1 gene within the genus Peromyscus. Sequence analysis of cloned ID elements in Peromyscus show most ID elements in this genus arose prior to Peromyscus subgenus divergence. Correspondence of the consensus sequence of individual ID elements in gerbil and deer mouse further confirms BC1 as a master gene in ID amplification. Several possible mechanisms responsible for the quantitative variations are explored.

Effect of Sodium on Seed Choice by Deer Mice, White-Footed Mice, and Hispid Cotton Rats

Effect of sodium content on seed use was tested for deer mice (Peromyscus maniculatus), white-footed mice (P. leucopus), and hispid cotton rats (Sigmodon hispidus) using sodium-enriched pearled barley seeds (Hordeum vulgare). Each trial included the choice of four types of barley seeds [ 1.6 (control), 4.8, 7.1, and 16.8 mg sodium/g seed]. Seed use by deer mice and whitefooted mice differed with sodium concentration but was not affected by locality (eastern versus central Kansas) or gender. In contrast, seed use by cotton rats was not influenced by sodium content and, although seed use differed between males and females (females tested were larger than the males), relative use of seed types was not affected by gender. Average sodium concentration of seeds used did not differ with locality or gender for either deer mice or white-footed mice, or among deer mice (6.6 mg/g), white-footed mice (5.6 mg/g), and cotton rats (6.2 mg/g). Mammalian herbivores, including ungulates (Dalke et al., 1965; Hebert and Cowan, 1971), lagomorphs (Smith, Latherland, and Myers, 1978), and arvicoline rodents (Christian, 1989; Hansson, 1990), periodically use mineral licks or eat sodium-rich materials. Laboratory tests also have shown a positive effect of sodium on food choice by small herbivorous rodents (Batzli, 1986). Further, use of sodium-soaked wooden pegs presented to free-living fox squirrels (Sciurus niger) and woodchucks (Marmota monax) demonstrated a positive sodium response by both of these sciurid rodents (Weeks and Kirkpatrick, 1978). We tested use of NaCl-rich foods by free-living deer mice (Peromyscus maniculatus), white-footed mice (P. leucopus), and hispid cotton rats (Sigmodon hispidus). Because one cannot determine which small, free-living species of rodent has fed on test materials placed in natural environments, we used a chamber, essentially a large live trap, in which test foods were SCorresponding author. This content downloaded from 157.55.39.163 on Wed, 21 Sep 2016 04:39:04 UTC All use subject to http://about.jstor.org/terms 144 TRANSACTIONS OF THE KANSAS ACADEMY OF SCIENCE available to trapped rodents. Our objectives were to test for an effect of sodium content on food use by these small rodents and possible interspecific differences in food choice related to sodium content. We expected rodents to eat sodium-enriched seeds but not to maximize sodium intake by eating only our highest sodium-enriched seeds (a concentration several times greater than natural seeds). We also expected a greater sodium content in ingested seeds for the cotton rat, a herbivore, than deer mice and white-footed mice,

Melatonin binding sites in sciurid and hystricomorph rodents: studies on ground squirrels and guinea pigs

Little is known about the distribution of binding sites for the pineal hormone melatonin in non-myomorph rodents. We used 2-[ 125I]iodomelatonin (IMEL) to analyze the distribution, affinity, and specificity of binding sites in the golden-mantled ground squirrel, a sciurid rodent that reportedly lacks IMEL binding sites in the brain. Specific binding was found not only in the pars tuberalis, but also in several telencephalic areas including the hypothalamic suprachiasmatic region. The affinity and specificity of IMEL binding are comparable to those reported in other rodents. IMEL binding studies in a hystricomorph rodent, the guinea pig, revealed high concentrations of receptor in the nucleus accumbens and dorsolateral thalamus. Central melatonin binding sites have now been demonstrated in species of all three rodent families. The heterogeneous distribution of melatonin receptors appears similar in the species studied, and no evidence is found to link IMEL binding sites at any particular locus to photoperiodic, circannual, or non-seasonal breeding patterns.

Essay on Contemporary Issues in Ethology: Variation among Mammalian Alarm Call Systems and the Problem of Meaning in Animal Signals

AbstractUnderstanding the information conveyed by animal signals requires studies of both production and perception. It is important to determine the relationship between signal morphology and the circumstances of production, the way signaller behavior varies with motivational state and the role of context in mediating responses to signals. Alarm calls are well‐suited to research of this type because they are widespread in birds and mammals and typically evoke unambiguous responses. We review studies of alarm calling in primates and ground‐dwelling sciurid rodents, concentrating especially on whether these signal systems may be viewed as ‘functionally referential’, that is, as conveying sufficient information about an event for receivers to select appropriate responses. Comparisons of the physical, behavioral and habitat characteristics of these species suggest that incompatibility of the escape responses required to avoid different classes of predators may have been an important factor in the evolution of functionally referential alarm calls.

Cuticular markings in species differentiation ofStreptopharagus(Nematoda-Spiruroidea) parasitic in rodents

Species of Streptopharagus, parasitic in rodents, show a great similarity in cephalic structures of males and females and in male reproductive organs, making taxonomic separation difficult. In the present communication species are differentiated by cuticular morphology: the number (0-2) of longitudinal alae and the distribution of interstriai, irregularly spaced, short, longitudinal ridges.Two new species are discribed, 2-are rediscribed and some observations on cuticular markings are added to the original description of a fifth one. S. numidicus Seurat, 1917, parasitic in Gerbillus pyramidum and G. gerbillus in Africa, is characterized by absence of longitudinal alae and the presence of the interstriai ridges over the entire body. Pharynx looped.S. kutassi (Schulz, 1927) Chabaud, 1954, from Citellus fulvus and Meriones persicus in Iran, found also by Schulz in four species of sciurid rodents over an area extending from Ukraine to Central Asia (Turkmenistan), has one (left) longitudinal ala and interstriai ridges only in the anterior part of the body. Pharynx bent.S. lerouxi Quentin, 1965, parasitic in Tatera lobengulae in the Congo, has one (left) logitudinal ala and a cuticle devoid of interstrial ridges. Pharynx looped S. greenbergi n. sp., found in 12 species of murid and gerbillid rodents in southern Israel, in the Sinai peninsula and in Egypt, has two longitudinal alae and interstriai ridges only in the anterior part of the body. Pharynx bent.S. schmidti n. sp., found in Meriones persicus in Iran, is characterized by two lateral alae and absence of interstriai ridges. Pharynx bent.

Further Observations on Estrus and Ovulation in Woodchucks (Marmota Monax) in Captivity1

The woodchuck is a seasonally breeding sciurid rodent. Female woodchucks are monoestrous and, when isolated from males, remain in a prolonged period of estrus characterized by a clear predominance of cornified cells in the vaginal smear. This study was designed to characterize relationships between the degree of vaginal cornification and sexual receptivity, and to study ovulation and related phenomena of this species in captivity. Fourteen individually caged adult females, maintained under standard laboratory conditions for 9-23 mo, were used in this investigation. Females exhibiting predominantly (67-97%) cornified smears were always receptive, regardless of the time interval from the onset of estrus, and mated within 24 h of pairing. Mated females allowed to complete pregnancy gave birth to live pups 30-32 days later. Litter size ranged from 3-7 pups. Serum progesterone (P) levels increased to approximately 2 ng/ml during the first week of pregnancy and greater than 5 ng/ml during the second and third weeks of pregnancy. Serum estradiol (E2) levels were elevated during the first week of pregnancy and began to decline thereafter. Examination of ovarian serial sections revealed that ovulation took place between 20 and 32 h after copulation. Serum levels increased significantly (4-fold) after ovulation (1.2 +/- 0.3 vs. 0.3 +/- 0.01 ng/ml). However, the circulating levels of E2 remained unchanged between the periods before (53 +/- 1 pg/ml) and after ovulation (60 +/- 3 pg/ml). Ovulation was not simultaneous in all mature follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Physical and behavioral postnatal development of woodchucks (Marmota monax)

The physical and behavioral postnatal development of woodchucks (Marmota monax) was analyzed from birth to 42 days of age, the age at which weaning begins. Postnatal growth was evaluated by means of daily measurements of body weight, body length, tail length, and length of hind foot. Data on length of ear pinnae, vibrissae, and fur, and on the timing of appearance of some events of physical development are also presented. We considered postnatal development of locomotion, alertness, exploratory behavior, feeding, and comfort and social behavior. Our results indicate no sexual dimorphism in body size in young woodchucks, despite its occurrence in adults. Intraspecific comparisons reveal that woodchucks from different populations show marked variation in growth rate. The high level of intraspecific variation in developmental rates of sciurid rodents provides a warning to those performing interspecific comparisons. The data also suggest that the ratio of growth rate to adult body weight is not related to environmental severity. Behavioral development in M. monax is similar to that of ground squirrels but faster than that of tree squirrels and flying squirrels. There is also no direct relationship between size and timing of behavioral development in sciurid rodents. The behavioral repertoire of young woodchucks is simpler than that of young Spermophilus lateralis, another asocial species. It is possible that specific differences in rates of development of social interactions led to such differentiation in the repertoire of social behavior.

Torpor Bout Duration during the Hibernation Season of Two Sciurid Rodents: Interrelations with Temperature and Metabolism

Torpor bouts of mammalian hibernators are generally shorter at the beginning and end and are consistently longer during the main part of the hibernation season. Because it is not known why the duration of torpor bouts changes at the beginning and end of the hibernation season, we studied this phenomenon in two sciurid rodents: Spermophilus saturatus (200–300g) and Eutamias amoenus (45-60g). We examined the seasonal change in torpor bout duration during hibernation at a constant air temperature (Ta) of 2° C in relation to (1) the minimum body temperature (minimum Tb) to which the animals could be experimentally cooled before they maintained a constant Tb or began to arouse, (2) Ta at the time of minimum Tb (minimum Ta), and (3) oxygen consumption (V̇o2) of torpid individuals at Ta 2° C. Average duration of torpor bouts during the main part of the hibernation season was about 11 d in S. saturatus and 8–9 d in E. amoenus; in response to experimental cooling, minimum Tb of both species declined as low as −0.2° C. In early and late hibernation, when torpor bouts were short, minimum Tb, minimum Ta, and V̇o2 during torpor were higher than in the main part of the hibernation season. Regression analyses suggest that minimum Tb and minimum Ta are more strongly correlated with torpor bout duration than V̇o2 in both species.

Variation in renal structure and urine concentrating capacity among ground squirrels of the Spermophilus townsendii complex (rodentia: sciuridae)

1. 1. Renal structure and urine concentrating capacity varied significantly among nine populations of desert ground squirrels representing four closely related taxa. 2. 2. Variation in renal structure was weakly associated with taxonomic grouping. 3. 3. Urine concentrating capacity was not correlated with standard measures of habitat aridity, but it was correlated with soil salinity. 4. 4. Maximum urine osmolalities for one population from the most saline habitat were among the highest documented for sciurid rodents. 5. 5. Results do not support the hypothesis that hibernating sciurids have poor renal efficiency.

Patterns of progesterone secretion in free-living California ground squirrels (Spermophilus beecheyi).

During a long-term field study of a free-living population of California ground squirrels (Spermophilus beecheyi), blood samples were drawn at regular intervals from marked females via femoral venipuncture, and plasma progesterone (P) and prolactin (PRL) were measured by radioimmunoassay. Marked fluctuations with season and reproductive condition occurred in circulating levels of both hormones, with peak levels occurring during the spring breeding season. Two peaks in P concentrations were observed each spring, the first occurring during pregnancy, and the second during lactation. Peak PRL levels in females were also reached during the lactation interval, midway between the two P peaks. Analysis of repeated measures from individual females showed a marked decline in circulating P around the time of parturition. Juveniles had lower mean P levels than adults, and yearlings had lower peak levels during their initial reproductive episodes than older females did. The observed pattern of P secretion in S. beecheyi differs from that known for most mammals, but resembles those reported for other ground-dwelling sciurid rodents.

Sciurid rodents (Mammalia) from the Chadronian and Orellan (Oligocene) of Nebraska

Upper dentition of Protosciurus mengi Black, from the Orellan Brule Formation, Nebraska, is described for the first time. The zygomatic plate is tilted anterodorsally, showing the beginnings of sciuromorphy as in the Arikareean species of this genus. A new genus of sciurid, Oligospermophilus, is named for the species originally identified as ?Protosciurus douglassi (Korth), based on additional material including a skull and upper dentitions. The zygomasseteric structure of O. douglassi is unlike any previously described Tertiary sciurid. The range of O. douglassi is extended from the late Chadronian to the Whitneyan. Three distinct lineages of sciurids, distinguished on dental morphology and zygomasseteric structure, can be traced in the Oligocene in North America; they are represented by the genera Protosciurus, Oligospermophilus, and ?Protosciurus.

Coccidia (Apicomplexa: Eimeriidae) from sciurid rodents (Eutamias, Sciurus, Tamiasciurus spp.) from the western United States and northern Mexico with description of two new species.

Since May 1979, 190 rodents in the family Sciuridae, representing three genera and nine species, have been collected in the western United States and northern Mexico and examined for coccidia; 71 (37%) had coccidian oocysts in their feces. These included 2 of 12 (17%) Eutamias canipes; 7 of 12 (58%) E. dorsalis; 18 of 50 (36%) E. merriami; 33 of 96 (34%) E. obscurus; 3 of 4 (75%) E. townsendii; 3 of 9 (33%) Sciurus aberti; 1 of 1 S. griseus; 1 of 1 Tamiasciurus hudsonicus mogollonensis; and 3 of 5 (60%) T. mearnsi. The following coccidians were identified from infected rodents: Eimeria cochisensis n. sp. and Eimeria dorsalis n. sp. from E. canipes, E. cochisensis, E. dorsalis, and E. tamiasciuri from E. dorsalis, E. dorsalis and E. tamiasciuri from E. merriami; E. cochisensis, E. dorsalis, E. tamiasciuri, and E. wisconsinensis from E. obscurus; E. cochisensis and E. dorsalis from E. townsendii; E. ontarioensis and E. tamiasciuri from S. aberti; E. tamiasciuri from S. griseus; E. tamiasciuri and E. toddi from T. h. mogollonensis; and E. tamiasciuri from T. mearnsi. Sporulated oocysts of Eimeria dorsalis n. sp. were ovoid, 21.9 x 16.8 (17-24 x 14-20) micrometer with sporocysts ovoid, 11.5 x 6.9 (10-14 x 6-8) micrometer. Sporulated oocysts of Eimeria cochisensis n. sp. were spheroid to subspheroid, 16.7 x 15.3 (15-18 x 14-17) micrometer, with sporocysts ovoid, 8.4 x 5.6 (6-11 x 4-7) micrometer. Fifty-five of 71 (77%) infected hosts had oocysts of only one eimerian species in their feces at the time they were examined. One eimerian, E. tamiasciuri, was found in seven of nine host species in three genera. A list is provided of all eimerians (22, including the species described here) that have been described in the literature from Eutamias, Sciurus, and Tamiasciurus spp.