Rodent-gnawed carbonate rocks from Indiana.ABSTRACT
Two carbonate-rock specimens from Jasper County and Monroe County, Indiana Monroe County is a county located in the U.S. state of Indiana, and determined by the U.S. Census Bureau to include the mean center of U.S. population in 1910. As of 2004, the population is 121,013. The county seat is Bloomington. Geography
According to the U.S. , are marked superficially by numerous grooves left by lower incisors of modern rodents. The Jasper County specimen is a calcitic dolomite dolomite (dō`ləmīt', dŏl`ə–).
1 Mineral, calcium magnesium carbonate, CaMg (CO3)2. , with incisor incisor /in·ci·sor/ (I) (-si´zer)
1. adapted for cutting.
2. incisor tooth.
n. marks most closely matching size ranges for Sciurus (?)carolinensis (gray squirrel), Tamias striatus Tamias striatus
see chipmunk. (eastern chipmunk chipmunk, rodent of the family Sciuridae (squirrel family). The chipmunk of the E United States and SE Canada is of the genus Tamias. The body of the common Eastern chipmunk, Tamias striatus, is about 5 to 6 in. ) and mouse-sized species. The Monroe County specimen is dolomitic dol·o·mite
1. A white or light-colored mineral, essentially CaMg(CO3)2, used in fertilizer, as a furnace refractory, and as a construction and ceramic material.
2. limestone showing marks in the size range of Sciurus niger (fox squirrel), Marmota monax (woodchuck woodchuck or groundhog, common name of a North American species of marmot, Marmota monax. This large rodent is found in open woods and ravines throughout most of Canada and the NE United States. ), mouse-sized species, and possibly the lagomorph Sylvilagus floridanus (eastern cottontail). Both rocks contain an abundance of calcium, magnesium and clay minerals which may have been a source of nutrients for the rodents, but also contain significant amounts (ca. 20%) of Si[O.sub.2] (quartz), which may act as a fine abrasive for wearing down ever-growing incisors. Weathering has softened the surface of both rock samples, thus facilitating the gnawing activity and perhaps explaining why several different species selected these particular rocks upon which to gnaw. It is also possible that once rodents had gnawed and deposited their scent on the rocks, other rodents would be attracted to inspect and gnaw the rocks in turn. However, there is as yet no record of such behavior among Indiana rodents.
Keywords: Gnaw marks, rodents, Ramp Creek, Rockford Limestone.
It is well-known that members of the Order Rodentia, whose name translates to "the gnawers," will chew on bones in the wild, and that "pest" species, such as Mus musculus (house mouse), chew through wood, plastic and many other materials they encounter. By comparison, the gnawing of rocks by rodents is rarely observed. Cuffey & Hattin (1965) reported gnawing of chalk by Sylvilagus audobonii (desert cottontail); and Gow (1992) observed African porcupines, presumably pre·sum·a·ble
That can be presumed or taken for granted; reasonable as a supposition: presumable causes of the disaster. Hystrix, gnawing a siltstone siltstone
Hardened sedimentary rock that is composed primarily of angular silt-sized particles (see silt) and that is not laminated or easily split into thin layers. ledge. Apart from these references, few or no studies have focused on rock-gnawing and its importance. Samples of carbonate rock from two Indiana counties situated about 200 km apart show significant modification of rock surfaces by rodent gnawing. The marks were probably produced within a few years' time because, in the Indiana climate, limestone erodes readily with exposure to the elements; and such marks are likely to be dulled or obliterated within a relatively short time.
Gnaw marks appear as paired, in some places divergent, grooves of wide-ranging size. The marks show the scoop-like, U-shaped cross-section typical of lower incisors rather than the flat-edged cross-section left by upper incisors (Burns et al. 1989). Imprints of upper teeth, left when the rodent braces its upper incisors against the gnawed surface (Burns et al. 1989), are not preserved. In rodents, the mandibular mandibular
adj pertaining to the lower jaw. symphysis symphysis /sym·phy·sis/ (sim´fi-sis) pl. sym´physes [Gr.] fibrocartilaginous joint; a type of joint in which the apposed bony surfaces are firmly united by a plate of fibrocartilage. between the lower incisors spreads as the jaw muscles contract. This causes the teeth to diverge and function as tweezers tweezers An instrument with pincers used to grasp or extract. See Optical tweezers. , and enables the rodent to scrape around corners, so that the lower incisors are more maneuverable than the uppers and are the pair most often used to gnaw. Rodents which burrow through hard-packed soils use lower incisors rather than uppers (Burns et al. 1989; Zuri et al. 1999), so lower incisors are more likely to be used on hard rock. The Indiana samples suggest gnawing activity by more than one rodent species, as the tooth marks vary greatly in size. This study is aim ed at identifying tooth marks to rodent taxa taxa: see taxon. , and investigating whether rodents gnaw for nutritional purposes, for wearing down their teeth, or both, and whether gnawing is a response to local environmental conditions or implies more widespread behavior and physiological needs.
To identify rodent taxa which might have produced the tooth marks on the Jasper and Monroe County carbonate-rock samples, widths of various-sized single and paired grooves were measured on each sample and compared with lower incisor widths from several species of rodents and lagomorphs known to be common in these counties. Rare taxa, or those with incisor widths well outside the range suggested by the tooth marks on the rocks, were not included. Mandibles from Indiana species were placed directly against the tooth marks on the rocks to find an approximate size match before they were measured. Skeletal specimens, used in this study are part of the mammal collections in the Zooarchaeology Laboratory at Indiana University Bloomington, with the exception of one Marmota monax skull from the Division of Mammals in the University of Kansas Natural History Museum This article or section needs sources or references that appear in reliable, third-party publications. Alone, primary sources and sources affiliated with the subject of this article are not sufficient for an accurate encyclopedia article. . Incisors were measured in place in alveoli Alveoli
Small air sacs or cavities in the lung that give the tissue a honeycomb appearance and expand its surface area for the exchange of oxygen and carbon dioxide. , and each tooth or pair of teeth was measured as close to the occlusal occlusal /oc·clu·sal/ (o-kloo´z'l)
1. pertaining to the masticating surfaces of the premolar and molar teeth.
1. (gnawing) edge as possible. All measureme nts were made to the nearest 0.1 mm with dial calipers.
Mandible mandible /man·di·ble/ (man´di-b'l) the horseshoe-shaped bone forming the lower jaw, articulating with the skull at the temporomandibular joint.mandib´ular
n. specimens used were as follows; they are in the Indiana University Bloomington Zooarchaeology Laboratory unless otherwise specified. "IU" refers to Indiana University Bloomington; "KU" refers to the Division of Mammals, University of Kansas Natural History Museum. The specimens were: Marmota monax: IU 901152, 9310936, 9510208, 9610169, 9710153, A3, A51, AA32, BB16, M1, M6, K23, K76, S83, S94, T22; KU RMT RMT right mentotransverse (position of the fetus).
RMT 1. Registered Massage Therapist 2. Renal mesenchymal tumor 4126. Sciurus niger: IU 84152, 84154, 84156, 84159, 841119, 841146, 8410067, 921225, 9110587, 9310582, 9310595, 9810182, HH76; immature specimens IU 369, 891382, 891383, 9610128, EE7. Sciurus carolinensis: IU 84122, 84124, 9610225, 9610226, D72, J16; immature specimens IU 9710476, M26. Tamias striatus: IU 84141, 9710371, EE61, W98, also one unnumbered specimen; immature specimen IU DD2O. Rattus norvegicus: IU AA54; Peromyscus maniculatus: IU S91; Peromyscus leucopus Peromyscus leucopus
deermouse; called also white-footed mouse. : IU 9810007; Zapus hudsonicus: IU FF79.
Description of rock samples.--Specimens of rodent-gnawed rock which are the principal basis for this study consist of impure im·pure
adj. im·pur·er, im·pur·est
1. Not pure or clean; contaminated.
2. Not purified by religious rite; unclean.
3. Immoral or sinful: impure thoughts. , fine-grained carbonate rocks, including one sample from the lower Mississippian Rockford Limestone and one from the middle Mississippian Ramp Creek Formation. The Rockford specimen is a much-weathered, mostly dark yellowish-orange (10 YR 6/6 on Geological Society of America The Geological Society of America (or GSA) is a nonprofit organization dedicated to the advancement of the geosciences. The society was founded in New York in 1888 by James Hall, James D. Rock-color Chart) calcitic dolostone n. 1. a stone or rock entirely composed of the mineral dolomite. , as determined from acid-reaction tests (Low 1951), thin sections, and x-ray diffraction analysis. This rock has a primarily microcrystalline microcrystalline /mi·cro·crys·tal·line/ (-kris´tah-lin) made up of minute crystals.
made up of minute crystals. texture, with grayish-colored patches of micrite which do not react to alizarin red S solution. A small part of the rock comprises coarsely crystalline calcite calcite (kăl`sīt), very widely distributed mineral, commonly white or colorless, but appearing in a great variety of colors owing to impurities. containing abundant silt and very fine sand-sized dolorhombs. Accessory components include silt-sized quartz (Si[O.sub.2]) grains, which are locally abundant, and silicified si·lic·i·fy
v. si·lic·i·fied, si·lic·i·fy·ing, si·lic·i·fies
To convert into or impregnate with silica.
To become converted into or impregnated with silica. skeletal remains derived primarily from crinoids that are scattered irregularly throughout. A small sample of this specimen was digested in hydrochloric acid (HCI (Human Computer Interaction) Refers to the design and implementation of computer systems that people interact with. It includes desktop systems as well as embedded systems in all kinds of devices. ), producing an insoluble residue amounting to 21.17% of the rock. X-ray diffraction analysis of the residue shows quartz as the dominant residue component, with scarcely more than trace quantities of magnesium calcite (Ca, Mg)[CO.sub.3] and the clay mineral illite Illite is a non-expanding, clay-sized, micaceous mineral. Illite is a phyllosilicate or layered silicate. Structurally illite is quite similar to muscovite or sericite with slightly more silicon, magnesium, iron, and water and slightly less tetrahedral aluminium and interlayer ([KAl.sub.2]([OH.sub.2]). [Al[Si.sub.3][[(O,OH).sub.10]]). This specimen, which is almost completely covered with tooth marks (Fig. 1), was collected by N. Gary Lane from a ditch near the center of section 21, T 27N, R 7W, Jasper County, Indiana Jasper County is a county located in the U.S. state of Indiana. As of 2000, the population was 30,043. The county seat is Rensselaer6. This county is part of the Chicago metropolitan area. History
Jasper County was formed in 1838. It was named for Sgt. . The locality and rock section are described by Gutschick & Treckman (1957).
The Ramp Creek sample is a moderate yellowish-brown (10 YR 5/4) dolomitic limestone as determined by the same testing methods used on the Rockford sample. This rock has a very fine grained microsparry matrix, in which are scattered very fine sand- and silt-sized rhombs of dolomite (Mg[CO.sub.3]), mostly silt-sized angular grains of quartz, and sand-to very fine gravel-sized skeletal grains derived from crinoids. The skeletal grains retain their calcitic composition, as determined from optical and staining techniques. As with the Rockford sample, a small portion of this sample was digested in hydrochloric acid, producing an insoluble residue representing 20.59% of the original rock. X-ray diffraction analysis of the residue shows quartz as the overwhelmingly predominant residue component, with little more than trace quantities of magnesium calcite, illite, and kaolinite kaolinite (kā`əlĭnīt), clay mineral crystallizing in the monoclinic system and forming the chief constituent of china clay and kaolin. ([Al.sub.2][Si.sub.2][O.sub.5][([OH.sub.4]) in decreasing order of abundance. The Ramp Creek sample was collected in 1984 by former Indiana Un iversity student David Kring from a Monroe County locality believed to be at the east edge of Bloomington, Indiana, near the intersection of State Road 45 and Smith Road.
The Jasper County specimen measures 18.4 cm long and 29.8 cm wide, with roughly 50% of one surface marked by small, paired scrape- or groove-like tooth marks (Fig. 1). Gnawed portions and other relatively fresh surfaces are dark yellowish-orange, whereas more weathered portions appear yellowish-gray. The rock is soft, crumbling away slightly with handling so as to leave orange-colored dust on the fingers, and is easily scratched with a fingernail fin·ger·nail
The nail on a finger. .
On the Jasper County specimen, paired gnaw-marks display a wide range of sizes. At least two sets of marks on this and the Monroe County sample diverge along their length, indicating the spreading of the mandibular symphysis (Fig. 1). Width of single tooth marks ranges from 0.2-1.1 mm, with a majority of marks being 0.9-1.0 mm across (Table 1). Width of paired marks ranges from 1.3-3.3 mm, with most pairs approximating 2.2 mm. Comparison with tooth measurements averaged for each Indiana rodent species suggests that 50% of measured marks correspond to lower incisor width of some species of Sciurus, possibly S. carolinensis (gray squirrel), incisor width, whereas about 25% match lower incisors of Tamias striatus (eastern chipmunk). There is one group of small tooth marks of ca. 0.5-0.9 mm single and 1.2-1.5 mm paired width (Fig. 1; Table 1) that appear to match tooth size of smaller Indiana rodents, such as Peromyscus maniculatus (deer mouse), Peromyscis leucopus (white-footed mouse), Zapus hudsonicus (meadow j umping mouse), Microtus pennsylvanicus (meadow vole vole, name for a large number of mouselike rodents, related to the lemmings. Most range in length from 3 1-2 to 7 in. (9–18 cm) and have rounded bodies with gray or brown coats, blunt muzzles, small ears concealed in the long fur, and short tails. ), Microtus orchrogaster (prairie vole), Microtus pinetorum (woodland vole) and Mus musculus (house mouse).
The limestone specimen collected from Monroe County, Indiana is smaller than the Jasper County specimen, measuring 12.0 cm in length and 9.6 cm in width (Fig. 2). A rough sketch, presumably made by the collector, accompanies the specimen and indicates that the gnawed sample was collected on a steep slope beneath an overhanging ledge of bedrock. Tooth marks occur only on one side of the rock specimen and cover about 75% of that surface (Fig. 2).
This sample is comparable to the Jasper County specimen in texture, fossil content, and relative hardness, but the surface appears to have been scraped nearly smooth by gnawing, and the rock is less crumbly crum·bly
adj. crum·bli·er, crum·bli·est
Easily crumbled; friable.
Adj. 1. than the Jasper sample. The gnawed surface is less weathered than in the Jasper County sample, and tooth marks are comparatively larger. Approximately 35% of measured marks are ca. 1.8- 2.0 mm single and 3.4-5.5 mm paired width and correspond most closely in size to Sciurus niger (fox squirrel) incisors. Another 35% of measured marks are relatively large, ca. 3.4- 4.8 mm single and 5.5 mm paired width, and match Marmota monax (woodchuck) incisors (Table 1). Smaller marks of ca. 0.6-0.9 mm single and 1.7-2.1 mm paired width (Fig. 2) may be from smaller fox squirrel individuals and from smaller, mouse-sized species, as in the Jasper County specimen. One pair of marks appears to show a central groove (Fig. 2), which may correspond to the upper incisors of a lagomorph (see Cuffey & Hattin 1965). Sylvilagus flo ridanus (eastern cottontail) is the most likely species to occur in Monroe County, and may have produced this pair of marks.
Identifications of gnawing taxa for the two Indiana carbonate-rock specimens are estimates at best. Some of the marks measured in this study fall into the size range of Sylvilagus floridanus lower incisors, which would look exactly like rodent incisor marks because they lack the central groove of rabbit upper incisors. However, aside from one set of marks on the Monroe County specimen described above, none of the marks shows distinct central grooves, and all are assumed to have been made by rodents. Unequivocal correlation of species to tooth marks is probably impossible, as the soft, crumbly limestone does not provide sharp distinction of marks; and many Indiana rodents share roughly the same range of tooth size. Additional research, such as live-trapping or analysis of carnivore carnivore (kär`nəvôr'), term commonly applied to any animal whose diet consists wholly or largely of animal matter. In animal systematics it refers to members of the mammalian order Carnivora (see Chordata). scat and owl pellets from the two specimen localities could provide a cross-section of local rodent populations and aid in identification of tooth marks.
Preliminary observations of rock-gnawing.--Three female Rattus norvegicus (domestic Norway rats - relatively recent immigrants to the United States) were kept to see whether captive rodents will gnaw on rocks, and if so, how often. The rats were approximately three weeks old when obtained. They were fed a diverse diet, including fruits, vegetables, grain cereal and rat pellets. If gnawing on various foods is sufficient to wear down incisors, as implied in Zuri et al. (1999), rat pellets and seeds are hard enough to serve this purpose for captive rodents. The pellets are also fortified fortified (fôrt´fīd),
adj containing additives more potent than the principal ingredient. with vitamins and minerals, including [CaCO.sub.3] so that the rats' diet had no severe deficiencies. One piece each of the Jasper and Monroe County rock specimens was placed in the rats' cage. Within the first few weeks, the rats left tooth marks on both rocks.
Gnawing occurred at night, for the rats slept throughout the day and were never observed gnawing the rocks. They gnawed selectively on corners and along edges of the specimens. On the Jasper sample they gnawed heavily on one relatively weathered side, and not at all on the other sides. After these first few weeks, no more new tooth marks were visible, and the rock surfaces which had been gnawed began to wear smooth from the rats' climbing over the rocks. Whereas they stopped gnawing the rocks, the rats often grated their upper incisors against the lowers, a habit common among caged rodents, and probably wild ones, that serves to hone the incisors and keep them worn down (Howard & Smith 1952). They also gnawed the bars of the cage.
In May 1999, a piece of Plattsmouth Limestone from the University of Kansas The University of Kansas (often referred to as KU or just Kansas) is an institution of higher learning in Lawrence, Kansas. The main campus resides atop Mount Oread. campus in Lawrence was placed against the wall of an apartment building just outside of campus, to see whether any wild rodents would chance to come and gnaw on it. Within a few days, a row of tiny tooth marks was observed along one sharp edge of the rock (Fig. 3). The tooth marks are in the size range of such small rodents as Peromyscus leucopus and Mus musculus, two species likely to live near human dwellings (Mumford & Whitaker 1982).
Rock-gnawing by rodents may be more common than has been assumed. Unless rodents gnaw repeatedly at one specific rock, their tooth marks are likely to be dispersed among many rocks and easily missed, especially if they are quickly erased by weathering. However, rock-gnawing is occasionally observed in the wild as a routine event. Karl W. Leonard (pers. commun. 1997) reported several instances in which Sciurus niger gnawed on Silurian Lockport Limestone at a corner of the Geology building on the campus of Kansas State University Kansas State University, main campus at Manhattan; coeducational; land-grant and state supported; chartered and opened 1863. There is an additional campus at Salina. Among the university's research facilities are the J. R. in Manhattan, Kansas. It is possible that the rock samples from Indiana were likewise visited on separate occasions.
Based upon preliminary observations, captive Rattus norvegicus gnaw preferentially along edges and on freshly exposed, relatively crumbly surfaces. Although rock and other hard substances abrade a·brade
1. To wear away by mechanical action.
2. To scrape away the surface layer from a part.
abrade ( rodent incisors quickly (Burns et al. 1989), the fact that the rats barely used the rock for a long period of time indicates that it was not needed to grind down incisors, at least not on a regular basis. This is particularly evident because, assuming that these activities are to wear down teeth and are not simply due to boredom, the rats continued to gnaw the cage bars and grate their teeth long after they stopped using the rock. Whether only one individual rat produced all the tooth marks, or whether gnawing activity to obtain calcium or magnesium would increase due to pregnancy and/or lactation lactation
Production of milk by female mammals after giving birth. The milk is discharged by the mammary glands in the breasts. Hormones triggered by delivery of the placenta and by nursing stimulate milk production. , are among questions remaining to be addressed using captive rats. Whether the piece of Plattsmouth limestone sample placed outdoors and gnawed by a wild, mouse-sized rodent was simply put in a convenient spot, or attracted the rodent for physical or nutritional needs, remains uncertain.
Rodents may gnaw on rocks for various reasons, including need for minerals, need to wear down the teeth, or need to release stress. Several records show that rodents, lagomorphs and artiodactyls derive minerals directly from rocks. Sciurus niger and Marmota monax, both of which may have produced tooth marks on the Indiana rocks, are known to lick salt (NaCl) from roadsides during springtime in southern Indiana (Weeks & Kirkpatrick 1978; Mumford & Whitaker 1982). Presumably, however, the only minerals a rodent could obtain from the Jasper and Monroe County specimens are calcium, magnesium and possibly the clay minerals illite and kaolinite. Sylvilagus floridanus may eat clay soil on occasion (Mumford & Whitaker 1982), and Sylvilagus audobonii is known to have gnawed extensively on Ca-rich but Sipoor chalky limestone (Cuffey & Hattin 1965). Neotoma floridana (wood rat wood rat: see pack rat.
or pack rat
Any of 22 species (genus Neotoma, family Cricetidae) of rodents that are nocturnal vegetarians of North and Central American deserts, forests, and mountains. ), Hystrix sp. (African porcupine porcupine, in zoology
porcupine, member of either of two rodent families, characterized by having some of its hairs modified as bristles, spines, or quills. ) and Geomys bursarius (eastern pocket gopher) store and gnaw on bones, most likely to gain calcium, sodium, and phosphorus (Smith 1948; Duthie & Skinner 1986; Richards & Munson 1988; Gow 1992). Small rodent gnaw marks are common on accumulated fossil bones in deposits such as sinkholes, which suggests that rodents specifically seek calcium and other minerals for certain dietary needs.
The Jasper and Monroe County rocks are dominated by the minerals calcite ([CaCo.sub.3]) and dolomite (CaMg[([CO.sub.3]).sub.2]) and would be good sources of calcium and magnesium, thus possibly functioning as rodent "licks" similar to those reported by Jones & Hanson (1985) and Peterson (1955) for artiodactyls. Deer and elk licks, in particular, are rich in calcium and magnesium, which are leached from limestones into the soil (Jones & Hanson 1985). However, studies on Sciurus niger and Marmota monax in southern Indiana (Weeks & Kirkpatrick 1978) show that these species seek sodium much more frequently than they seek calcium and magnesium.
Nutritional needs probably vary among species, individuals and environments. For example, "salt drives" in Sciurus niger and Marmota monax are highest in springtime (Weeks & Kirkpatrick 1978). Calcium and magnesium may also be more sought after in springtime. Plants growing in carbonate soils, such as those which occur abundantly in Indiana, are naturally enriched in calcium (Jones & Hanson 1985), and perhaps in magnesium. Marmota monax eats mainly leaves and stems of plants and may derive much of the calcium and magnesium in its diet from those plants during their growing season. Upon emerging from hibernation in early spring when plants are scarce, M. monax may have a calcium/magnesium deficiency which could be compensated for by gnawing carbonate rocks. Sciurus niger is not primarily a plant-eater, yet it and Tamias striatus may still have calcium/magnesium deficiencies during the winter and early spring months. In addition, gravid gravid /grav·id/ (grav´id) pregnant.
Carrying eggs or developing young.
gra·vid or lactating lac·tate 1
intr.v. lac·tat·ed, lac·tat·ing, lac·tates
To secrete or produce milk.
[Latin lact females and growing juveniles may require larger amounts of th ese minerals than other individuals.
Alternatively, rodents gnawed the Indiana rocks to help wear down continually growing incisors. Observations of captive Rattus norvegicus seem to suggest that a rock is not required to wear down teeth on a routine basis, if the rodent habitually eats hard foods. Cuffey & Hattin (1965) discount gnawing to wear down teeth based on the softness of their gnawed chalk sample, which contained only about 1% [SiO.sub.2]. On the other hand, Gow (1992) observed Hystrix sp. gnawing on siltstone containing >1% calcium, which was "like a soft talc" and "easily scored by a fingernail," and suggested that the siltstone could serve as a fine abrasive polish for teeth. Limestone typically has a hardness of about 3. The enamel of rodent incisors contains iron and is therefore harder than the enamel of most mammal teeth. Thus, most carbonate rocks are probably too soft to wear down rodent incisors appreciably. However, as the Indiana samples contain ca. 20% [SiO.sub.2], they may provide a fine abrasive to help hone incisors. In any case, rodents gnawing these Indiana rocks probably subjected their lower incisors to wear, due to the relatively great amount of [SiO.sub.2] in the samples.
Why several different species selected the same Rockford and Ramp Creek samples for gnawing is an intriguing question. Both specimens have suffered considerable weathering such that the rock surfaces are soft and somewhat crumbly. Such a condition would make gnawing, especially for nutrients, an easy process and could explain why more than one species chose each of these rocks for its nutritional or tooth-wear needs. It is also probable that, once a rodent had gnawed and left its scent on the rock exposure, conspecifics and other species would be likely to approach the rock so as to leave their scent as well and gnaw at the rock, which would be covered with salty deposits from the other rodents.
Thus far, no studies of this type of behavior have been made; and further study is needed to determine the reasons why wild rodents gnaw on rocks, and the role carbonate rocks play in the ecology of Indiana rodents.
A dolomitic limestone sample from Monroe County and a calcitic dolostone sample from Jasper County, Indiana, were gnawed extensively by several species of rodents and possibly one lagomorph. Species identified to tooth marks on the rocks include Marmota monax, mouse-sized species, and possibly Sciurus niger and Sylvilagus floridanus (Monroe County specimen), and Sciurus ?carolinensis, Tamias striatus and mouse-sized species (Jasper County specimen). The reason for the gnawing behavior is still uncertain. We propose that the gnawed carbonates could have served as a source of calcium and/or magnesium. The rocks also contain significant amounts of abrasive [SiO.sub.2], which could help wear down rodent incisors. These needs may vary with specific habitat conditions, and further studies may demonstrate use of cacium and magnesium by pregnant or lactating rodents and rodents in seasonally or perpetually mineral-deficient areas. Preliminary observations show that both captive and wild small rodents readily gnaw on carbonate rocks placed in their environment. The rock-gnawing habit may thus extend to rodents in a wide variety of habitats, be a more common behavior than previously supposed, and be worthy of future experimental investigation.
Table 1 Comparison of lower incisor widths measured from skeletal specimens with widths of tooth marks on Indiana carbonate rock specimens. The number of marks measured represents the best-preserved sets of marks on each rock, and does not necessarily reflect total number of marks of that size. Because tooth mark widths are approximate owing to imperfect clarity, indentifications of rodent species are also estimates. All measurements are in mm. Range, single Rock specimen Rodent species incisor width Rockford Limestone Marmota monax (woodchuck) 2.1-4.1 Ramp Creek-Formation Sciurus Scurs niger (fox squirrel) 1.0-1.8 (Jasper County) Tamias striatus (eastern chipmunk 0.4-1.1 and/or mouse-sized species) Ramp Creek Formation Sciurus carolinensis (gray 0.8-1.3 (Monroe County) squirrel) Tamias striatus 0.4-1.1 Peromyscus leucopus (white-footed 0.7 mouse or P. maniculatus deer mouse) Zapus hudsonicus (meadow jumping 0.4 mouse) Rangem, paired Number of Range, single Rock specimen incisor width tooth marks tooth mark Rockford Limestone 4.9-9.7 5 3.4-3.8 Ramp Creek-Formation 2.4-4.1 5 0.9-1.8 (Jasper County) 1.3-2.6 2 0.6-0.9 Ramp Creek Formation 1.8-3.1 16 1.0-1.1 (Monroe County) 1.3-2.6 8 0.8-0.9 1.2 4 0.7 1.3 5 0.3-0.5 Range, paired Rock specimen tooth marks Rockford Limestone 5.5 Ramp Creek-Formation 3.4-4.4 (Jasper County) 1.7 Ramp Creek Formation 1.8-3.0 (Monroe County) 1.8-2.4 1.2-1.5 1.2-1.5
The authors thank W.R. Adams of the Indiana University Zooarchaeology Laboratory and R. Timm of the Division of Mammals, University of Kansas Natural History Museum, for access to skeletal specimens, and J.R. Dodd of the Indiana University Department of Geological Sciences for assistance and advice in processing and analysis of rock samples. Additional thanks are due J. Day of the Indiana Geological Survey Created in 1837, the Indiana Geological Survey (IGS) is an official agency of the U.S. state of Indiana charged with geological research and the dissemination of information about the state's energy, mineral and water resources. for photographic work, and W.S. Heath and A. Rode of the University of Kansas Department of Geology for identification of the Plattsmouth limestone sample.
Manuscript received 27 December 2000, revised 29 October 2001.
Burns, J.A., D.L. Flath & TW. Clark. 1989. On the structure and function of white-tailed prairie dog The White-tailed Prairie Dog (Cynomys leucurus) is found in western Wyoming and western Colorado with small areas in eastern Utah and southern Montana. The largest populations are in Wyoming. burrows. Great Basin Naturalist 49(4):517-524.
Cuffey, R.J. & D.E. Hattin. 1965. Kansas chalk gnawed by desert cottontail. Journal of Mammalogy The Journal of Mammalogy is the flagship publication of the American Society of Mammalogists. Both the society and the journal were founded in 1919. The peer-reviewed journal publishes papers about mammals throughout the world and their conservation. 46(4):696-697.
Duthie, A.G. & J.D. Skinner. 1986. Osteophagia in the Cape porcupine Hystrix africaeaustralis. South African Journal of Zoology The Journal of Zoology (not to be confused with a different journal called Zoology) is a scientific journal concerning zoology, the study of animals. It was founded in 1830 by the Zoological Society of London. External links
Gow, C.E. 1992. Gnawing of rock outcrop by porcupines. South African Journal of Geology 95(1/2):74-75.
Gutshick, R.C. & J.F. Treckman. 1957. Lower Mississippian cephalopods from the Rockford Limestone of northern Indiana. Journal of Paleontology The Journal of Paleontology is a scientific journal covering the field of paleontology, published by The Paleontological Society. It is indexed by BIOSIS Previews, Science Citation Index, The Zoological Record and GeoRef and has an impact factor of 0.4499 . 31(6):1148-1153.
Howard, W.E. & M.E. Smith. 1952. Rate of extrusive ex·tru·sive
1. Tending to push or thrust out.
2. Tending to protrude or project.
3. Derived from magma poured out or ejected at the earth's surface. Used of igneous rocks.
Adj. 1. growth of incisors of pocket gophers. Journal of Mammalogy 33(4):485-487.
Jones, R.L. & H.C. Hanson. 1985. Mineral Licks, Geophagy ge·oph·a·gy or ge·oph·a·gism or ge·o·pha·gia
The eating of earthy substances, such as clay or chalk, that is practiced as a custom or for dietary or subsistence reasons. Also called dirt-eating. , and Biogeochemistry bi·o·ge·o·chem·is·try
The study of the relationship between the geochemistry of a region and the animal and plant life in that region.
bi of North American Ungulates ungulates, ungulata
animals with hooves; cattle, sheep, goat, pig, horse and many wild and other domesticated species. . The Iowa State University Academics
ISU is best known for its degree programs in science, engineering, and agriculture. ISU is also home of the world's first electronic digital computing device, the Atanasoff–Berry Computer. Press, Ames. 301 pp.
Low, J.W. 1951. Examination of well cuttings. Quarterly of the Colorado School of Mines Colorado School of Mines, at Golden; state supported, coeducational; chartered 1874. It was one of the first mineral engineering schools in the United States. 46(4). 48 pp.
Mumford, R.E. & J.O. Whitaker. 1982. Mammals of Indiana. Indiana University Press Indiana University Press, also known as IU Press, is a publishing house at Indiana University that engages in academic publishing, specializing in the humanities and social sciences. It was founded in 1950. Its headquarters are located in Bloomington, Indiana. , Bloomington. 490 pp.
Peterson, R.L. 1955. North American Moose. University of Toronto Research at the University of Toronto has been responsible for the world's first electronic heart pacemaker, artificial larynx, single-lung transplant, nerve transplant, artificial pancreas, chemical laser, G-suit, the first practical electron microscope, the first cloning of T-cells, Press, Toronto. 280 pp.
Richards, R.L. & PJ. Munson. 1988. Flat-headed peccary peccary (pĕk`ərē), small wild pig, genus Tayassu, the only pig native to the Americas. Although similar in appearance to Old World pigs, peccaries are classified in a family of their own because of anatomical differences. (Platygonus) and recovered Quaternary quaternary /qua·ter·nary/ (kwah´ter-nar?e)
1. fourth in order.
2. containing four elements or groups.
1. Consisting of four; in fours. vertebrate fauna of Indun Rock Shelter, Monroe County, Indiana. National Speleological Society The National Speleological Society (NSS) is an organization formed in 1941 to advance the exploration, conservation, study, and understanding of caves in the United States. Originally located in Washington D.C., its current offices are in Huntsville, Alabama. Bulletin 50:64-71.
Smith, C.F 1948. A burrow of the pocket gopher (Geomys bursarius) in eastern Kansas. Transactions of the Kansas Academy of Science 51:313-315.
Weeks, H.P., Jr. & C.M. Kirkpatrick. 1978. Salt preferences and sodium drive phenology phe·nol·o·gy
1. The scientific study of periodic biological phenomena, such as flowering, breeding, and migration, in relation to climatic conditions.
2. in fox squirrels and woodchucks. Journal of Mammalogy 59(3):531-532.
Zuri, I., I. Kaffe, D. Dayan & J. Terkel. 1999. Incisor adaptation to fossorial fos·so·ri·al
Adapted for or used in burrowing or digging: the fossorial forefeet of a mole.
[From Late Latin life in the blind mole-rat, Spalax ehrenbergi. Journal of Mammalogy 80(3):734-741.