4209(55-64).pdf ALCES VOL. 42, 2006 CLOUGH ET AL. - ABNORMAL INCISOR BREAKAGE IN MOOSE 55 ELEMENTAL COMPOSITION OF INCISORS IN NOVA SCOTIA MOOSE: EVALUATION OF A POPULATION WITH ABNORMAL INCISOR BREAKAGE Michael Clough1,2, Marcos Zentilli1, Hugh G. Broders3, andTony Nette4 1Department of Earth Sciences, Dalhousie University, Halifax, NS, Canada B3H 4J1; 3Department of Biology, St. Mary’s University, Halifax, NS, Canada B3H 3C3, e-mail: hugh.broders@smu.ca; 4Nova Scotia Department of Natural Resources, Wildlife Division, Kentville, NS, Canada B4N 4E5 ABSTRACT: This study compared the concentrations of major and trace elements in the enamel of incisors from moose (Alces alces andersoni) in Cape Breton Highlands, where the incidence of incisor tooth breakage was believed to be unusually high, and moose in southwest Nova Scotia (A. a. ameri- cana) where there was no evidence of breakage. Our goal was to determine which elements, if any, might be related to the incisor breakage in moose from Cape Breton Highlands. There was a positive relationship between age and frequency of incisor breakage, and most moose had a broken I2 incisor by 4 years of age in the Cape Breton Highlands. We analyzed I2 incisors for 51 trace elements with Inductively Coupled Plasma-Mass Spectrometry. Concentrations of 8 elements, including barium, beryllium, cadmium, cobalt, lead, tin, strontium, and yttrium, were lower (P < 0.05) in incisors from Cape Breton Highlands; gallium had a higher concentration. Reduced intake of barium, beryllium, and ALCES VOL. 42: 55-64 (2006) Key words: Alces alces, barium, beryllium, cadmium, cobalt, gallium, incisor, Inductively Coupled Plasma-Mass Spectrometry, lead, moose, Nova Scotia, strontium, teeth, trace elements, yttrium The role that major and trace elements play in the metabolism of organisms has been the focus of intense, well-documented research (Underwood 1977, Prasad 1993, Underwood and Suttle 1999, Bogden and Klevay 2000). Disease may result from either a toxic or a (Maisironi 2000). Teeth are good indicators of the abundance of many elements (Brown et al. 2004, Kang et al. 2004, Dolphin et al. 2005) due to the crystal structure of enamel (Sharaway and Yeager 1991, Simmelink 1994). Major and trace elements are incorporated within the hydroxyapatite crystal framework during the mineralization period (Sharaway and Yeager 1991, Simmelink 1994) and, due to the semi- permeable nature of hydroxyapatite, small ions and molecules are able to pass through the enamel framework preceding eruption (Cutress 1983). Therefore, to an extent, teeth remain in chemical equilibrium with the oral environment (Zimmerman 1976, Driessens 1982). - enced by the concentration of major and trace elements (Zimmerman 1976), which is af- fected by various factors such as normal wear, food composition, and regional geochemistry (Cutress 1983). Therefore teeth are an ex- cellent bio-indicator of local environmental conditions (Lee et al. 1999, Lochner et al. 1999, Gdula-Argasinska et al. 2004). This is especially true for non-migratory ruminant 2Present address: Department of Biology, St. Mary's University, Halifax, NS, Canada B3H 3C3 ABNORMAL INCISOR BREAKAGE IN MOOSE - CLOUGH ET AL. ALCES VOL. 42, 2006 56 herbivores such as moose (Alces alces) that obtain their entire dietary mineral intake from distinct regional geological localities (Ceder- lund and Okarma 1988, Lepitch and Gilbert 1989, Hundertmark 1998). Observations of physical and behavioral anomalies suggest that the moose population is stressed in the Cape Breton Highlands (A. a. andersoni) in Nova Scotia, Canada. Wildlife authorities have observed osteophagia (Roger and Nette 2002), an increased incidence of bark stripping, and tooth breakage (Fig. 1) in Cape Breton Highlands moose where densi- ties are high and heavy browsing of preferred vegetation is evident. Distinct browse lines 2–3 meters off the ground extend several kilometers through the forest (Basquill and Thompson 1997). The only previously reported case of in- cisor breakage was in a moose (A. a. gigas) population on the Seward Peninsula, Alaska. Smith (1992) documented ‘incisiform break- age’ over a 2-year period (1988-1990), which closely resembles the breakage observed in Cape Breton Highlands moose. The break- age observed in the Cape Breton Highlands is markedly different from the tooth wear frequently reported in other ungulate species (Hewison et al. 1999, Loe et al. 2003). It also differs from the incisiform wear reported in Kenai Peninsula moose by Peterson et al. (1982), and the unusual wear described by Young and Marty (1986) in a Manitoban moose population. The distinctive incisor breakage begins as a brown stained crack on the tooth surface (Fig. 1) that is a precursor to break- age. Where breakage has occurred, the tooth is subsequently rounded down and stained brown. This rounded, staining characteristic is important because it indicates that break- age occurred during the lifetime and not at, or after, death. The purpose of this study was to determine whether concentrations of major and trace elements in incisors might explain breakage. To do this we compared trace element concen- trations of teeth from Cape Breton Highlands moose to those of a control population on main- land Nova Scotia (A. a. americana) without evidence of abnormal incisor breakage. STUDY AREAS The Highlands region is located in north- ern Cape Breton Island, in northeastern Nova Scotia, and covers an area of approximately 3,900 km2. The area is a characteristic boreal region (Pulsifer and Nette 1995) with a peak elevation of approximately 535 m above sea level (Canada: National and Historic Parks Branch 1970). Approximately 1,600 mm of precipitation is recorded annually, with > 400 cm falling as snow, resulting in snow pack that lasts 181-212 days (Phillips 1990). The control area was the Tobeatic Wilder- ness Area, which is a characteristic Acadian Forest Region (Farrier et al. 1991). The area receives approximately 1,400 mm of pre- cipitation annually, with 150-200 cm falling as snow, resulting in a snow pack that lasts 110-140 days (Phillips 1990). METHODS In the Cape Breton Highlands, incisor samples were obtained from hunters during the 2001 hunting season from management zones immediately north and south of Cape 1 2 3 Fig 1. Lower mandible from a Cape Breton Highlands moose. Numbers on teeth represent breakage scores. Note the stained, polished, and rounded surfaces of the fractured teeth indicating breakage occurred during lifetime of the animal (Photo by Vince Power, 2001). ALCES VOL. 42, 2006 CLOUGH ET AL. - ABNORMAL INCISOR BREAKAGE IN MOOSE 57 Breton Highlands National Park (Fig. 2). In the Tobeatic Wilderness area in southwestern Nova Scotia, incisors were obtained by the Nova Scotia Department of Natural Resources (NSDNR) from accidental kills, illegal kills, and live extraction when collaring animals as part of ongoing studies (Fig. 2). Based on the work of Smith (1992), Nette and Power (NSDNR 1999) devised a - ing the degree of incisor breakage used in this study: slight – indicates < 30% of tooth material missing from the incisal surface; moderate – indicates 30-60% of tooth material missing from the incisal surface; and severe – indicates > 60% of tooth material missing from the incisal surface. Individual I1s were used to determine age from cementum annuli measurements (Matson 1981). The concentrations of 37 elements and the 14 rare earth elements (REE) were determined from the I2s. The REE comprising the lan- thanide series were summed and considered as one element (Brown et al. 2000). The root was separated from the crown with a Buhler Isomet low speed saw with a diamond tip blade. Crowns were crushed with a percussion cutter and enamel fragments were retrieved tipped paintbrush. Enamel was reduced to a with ethanol as a lubricant. An ultrasound bath agate mortar pestle between samples to prevent cross-contamination. Enamel was placed in drying dishes and dried at room temperature for 3-5 hours, recovered, and placed into labeled vials. Samples were sent to Geo Labs labora- tory (Sudbury, Ontario, Canada) and analyzed for element content using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Two-sample t-tests were used to compare element concentrations of the two populations. Regression analysis was used to assess the relationship between age and breakage score (Sokal and Rohlf 1995) using 46 I2s collected during the 2001 hunting season. Age/breakage data compiled between 1996-2002 (NSDNR 2002) were analyzed using Chi-square analysis of breakage between the I1s and I2s. Statisti- RESULTS There was a positive relationship between incisor breakage and age in Cape Breton 1.28 + 0.158AGE, P < 0.05, R2 I1 had a higher frequency of breakage than the I2 ( 2 P frequency of breakage of I1 was 2-3x that of I2 at > 2.5 years old and 2 out of 3 moose had a broken I1 after 4.5 years. Breakage of I1 in moose > 3.5 years old was > 50% and more than doubled from 3.5 to 5.5 years old. Breakage of I2 was < 30% in moose < 6.5 years old (Table 1). Relative to the control population in south- west Nova Scotia, Cape Breton Highlands moose had lower (P < 0.05) concentrations of barium (Ba), beryllium (Be), cadmium (Cd), cobalt (Co), lead (Pb), strontium (Sr), tin (Sn), and yttrium (Y), and higher concentration of gallium (Ga) in the enamel of their teeth (Table 2). Largest absolute differences occurred in Fig. 2: Moose teeth sample collection areas in Nova Scotia, Canada. Note: No samples were taken from Cape Breton Highlands National Park indicated by the lined inset area. ABNORMAL INCISOR BREAKAGE IN MOOSE - CLOUGH ET AL. ALCES VOL. 42, 2006 58 Cd, Co, Pb, Sn, Sr, and Y. Although not dif- ferent, relatively large absolute differences were found in chromium (Cr), iron (Fe), and vanadium (V) (Table 2). DISCUSSION Breakage type and trends measured in Cape Breton Highland moose were similar to results from Alaskan moose that indicated that breakage severity increased with age, and breakage severity was greater in I1s than I2s (Smith 1992). There were no differences in elemental concentrations of 40 teeth collected from the Seward Peninsula and 20 teeth from a control population near Galena, Alaska (Smith 1992). The results for their microbeam analy- sis were not presented, therefore, comparisons between Nova Scotia and Alaska moose were in mineral requirements, diagnosis of problems (Underwood and Suttle 1999). However, the lower concentrations of Ba, Be, Co, Sr, and Y within the Cape Breton Highlands population are consistent with previous studies that concluded that a reduc- tion of these elements may result in higher enamel solubility and compromised strength that lead to dental disease (Bibby and Losee 1970, Curzon 1983a, b, c, d). Barium, Be, Co, and Sr depletion result in depressed growth, even evidence of hypoplasia within erythro- genic tissue and bone marrow (Underwood 1971, Curzon 1983a, d). Strontium may also that results in retardation of apatite dissolution (Curzon 1983d). - trations of Cd, Ga, Pb, and Sn may have on enamel strength and solubility are unclear (Curzon 1983c, Stack 1983a, b), although Sn may inhibit the dissolution of enamel via acid neutralization within the oral environ- ment (Curzon 1983c). Knowledge of es- sential vitamins and minerals within the diet of moose is limited (Schwartz and Renecker 1998). Frank et al. (2004) examined elemental concentrations from various tissues of Nova Scotia moose and found that Tobeatic moose displayed unusually high levels of Cd within kidney tissue as compared to Cape Breton Highlands moose; Cd concentration in enamel was also high in Tobeatic moose (Table 2). They also found that both Tobeatic and Cape Breton Highland moose had lower Co con- centrations than Swedish and Alaskan moose. These data and the low concentration value of Co in the Cape Breton Highlands population (Table 2) suggest that Nova Scotia populations Though not different, it is important to note that the relative concentrations of Cr, Fe, and V were low, and magnesium (Mg) high in the Cape Breton Highlands population (Table 2). With the exception of Mg, these results were not surprising because geochemical position within the periodic table (Albarede 2003). Elements of the same group would be expected to have similar, relative availability within the environment. Cadmium, Fe, and V are all grouped in the transition metals of the periodic table with Cd, Co, and Y that Age Incisor 1 Incisor 2 n Breakage frequency (%) n Breakage frequency (%) 1.5 210 2 (1.0%) 214 1 (0.5%) 2.5 282 33 (11.7%) 287 8 (2.8%) 3.5 299 98 (32.8%) 308 24 (7.8%) 4.5 228 122 (53.5%) 232 49 (21.1%) 5.5 118 86 (72.9%) 120 32 (26.7%) 218 148 (67.9%) 220 71 (32.3%) Table 1. Sample size, age, and frequency of in- cisor breakage of harvested moose from the Cape Breton Highlands, 1999-2002 (NSDNR 2002). ALCES VOL. 42, 2006 CLOUGH ET AL. - ABNORMAL INCISOR BREAKAGE IN MOOSE 59 Table 2. Element concentrations in tooth enamel from 2 moose populations in Nova Scotia, Canada. Concentrations are expressed in ppm (except Ca, which is expressed as weight percent). Bold num- Element Cape Breton Highlands, n Mainland (control) population, n Mean SE Range Mean SE Range Ag 0.055 0.015 0.011 - 0.294 0.063 0.012 0.038 - 0.089 Al 65.3 18 12.9 - 329 72.5 8.4 59.9 - 95.8 As 4.842 0.22 3.870 - 4.212 5.685 0.58 4.71 - 7.37 Ba 125.7 8.6 72.6 - 235 180.5 6.7 171 – 200 Be 0.015 0.002 0 - 0.034 0.029 0.01 0 - 0.045 Bi 0.015 0.003 0.005 - 0.058 0.024 0.006 0.017 - 0.041 Ca (WT%) 34.8 0.4 30.8 - 38.5 35.2 0.7 33.9 - 37.2 Cd 0.114 0.032 0.028 - 0.64 0.363 0.12 0.201 - 0.717 Co 0.017 0.015 0 - 0.297 0.824 0.31 0 - 1.15 Cr 0.082 0.024 0 - 0.323 0.18 0.065 0.096 - 0.37 Cs 0.005 0.001 0.02 - 0.019 0.008 0.001 0.006 - 0.001 Cu 17.4 2.6 5.4 - 48.5 24.3 2.2 18 - 28.7 Fe 143.7 44 41.7 - 914 308 111 176 – 639 Ga 0.207 0.007 0.144 - 0.267 0.169 0.009 0.144 - 0.182 Hf 0.011 0.004 0 - 0.072 0.017 0.014 0.001 - 0.060 Li 1.031 0.17 0.270 - 3.16 1.216 0.21 0.902 - 1.81 Mg 3429 155 2640 - 4720 2767.5 86 2590 – 2960 Mn 56.8 8.8 14.4 - 168 34.5 11 14.7 – 65 Mo 0.055 0.012 0.015 - 0.242 0.061 0.006 0.047 - 0.076 Nb 0.02 0.005 0.009 - 0.104 0.02 0.002 0.015 - 0.023 Pb 0.805 0.077 0.330 - 1.88 1.935 0.49 1.06 - 3.30 Rb 0.607 0.054 0.287 - 1.25 0.847 0.053 0.689 - 0.926 Sb 0.027 0.007 0.004 - 0.141 0.026 0.009 0.007 - 0.048 Se 1.349 0.029 1.115 - 1.74 1.425 0.027 1.37 - 1.48 Si 173.2 26 62.2 - 552 152 9.3 137 – 179 Sn 0.084 0.018 0.01 - 0.322 0.343 0.16 0.151 - 0.744 Sr 268.3 13 192 - 415 518.5 22 474 – 564 Ta 0.001 0.000 0 - 0.008 0.001 0.000 0 - 0.001 Th 0.004 0.001 0 - 0.018 0.009 0.003 0.004 - 0.018 Ti 88.6 4.7 70 - 153 84.6 6.3 70.9 - 97.9 Tl 0.008 0.001 0.005 - 0.015 0.008 0.001 0.006 - 0.011 U 0.003 0.001 0.001 - 0.015 0.006 0.001 0.004 - 0.008 V 0.387 0.045 0.168 - 0.982 0.597 0.098 0.353 - 0.824 W 7.61 1.7 0.99 - 20.8 4.16 1.4 1.88 - 8.39 Y 0.062 0.009 0.03 - 0.19 0.133 0.02 0.097 - 0.169 ABNORMAL INCISOR BREAKAGE IN MOOSE - CLOUGH ET AL. ALCES VOL. 42, 2006 60 had lower concentration in the Cape Breton Highlands population. However, the alkaline – earth metal Mg has a higher concentration in the Cape Breton Highlands population than the Tobeatic population, unlike the other alkaline earth metals (Ba, Be, and Sr). The reason for this is unclear, however it may be a result of isobaric interference during the ICP-MS analy- sis, which is a common issue with biological applications (Taylor et al. 2005). - lying cause for the incisor breakage observed in the Cape Breton Highlands moose popula- tion. Osteophagia is generally considered to occur within ruminant species as a result of - rette 1985, Denton et al. 1986). Bark stripping by moose is generally considered to be a sign of starvation (Renecker and Schwartz 1998), and heavily browsed plants generally contain less nutritive value for moose (Schwartz and Renecker 1998). It is important for moose to consume a wide variety of plant species, or (Ohlson and Staaland 2001). Whether tooth breakage is a result of osteo- phagia or bark stripping, or even a combination of the two, is unclear. However, these phe- nomena have been well documented in other ungulate species (Bowyer 1983, Barrette 1985, Denton et al. 1986, Duthie and Skinner 1986, Kierdorf 1994, Baker et al. 1997, Yokoyama et al. 2001, Ueda et al. 2002) with no reports of breakage similar to that observed in Cape Breton Highlands moose. It was interesting that teeth from the con- trol area were consistently richer in tin by one differences in bedrock geology. Southwestern economic) deposits of tin and the glacial deposits and soils are locally enriched with this and other elements common in granitoid intrusive rocks. This correlation of enamel geochemistry and bedrock geology may have valuable forensic usefulness. Continued use of a broken incisor results in the incisal surface becoming rounded (Fig.1) and this probably reduces foraging likely has negative implications for the overall health and vitality of individual moose. To on population dynamics, it would be neces- sary to compare the mortality rate of older age classes and population age structure of several moose populations. We suggest that research on incisor breakage in the Cape Breton Highlands moose continue and be supplemented with more control samples from other populations. ACKNOWLEDGEMENTS We would like to thank Vince Power (NSDNR) for supplying hunting data, fre- quency and breakage data, and photos of moose mandibles. Alexander (Sandy) Grist trained MC in sample preparation techniques in the Fission Track Research Laboratory of Dalhousie University. During its early stages - tions by Prof. Milton Graves, Phil Casey Element Cape Breton Highlands, n Mainland (control) population, n Mean SE Range Mean SE Range Zn 54.7 3.3 37.9 - 85.9 64.6 5.6 53.6 - 80.3 Zr 0.456 0.19 0.027 - 3.35 0.865 0.8 0.027 - 0.084 REE 0.301 0.1 0.076 - 2.196 0.899 0.41 0.271 - 0.711 Table 2 (continued). Element concentrations in tooth enamel from 2 moose populations in Nova Scotia, Canada. Concentrations are expressed in ppm (except Ca, which is expressed as weight percent). ALCES VOL. 42, 2006 CLOUGH ET AL. - ABNORMAL INCISOR BREAKAGE IN MOOSE 61 and BSc. Honours thesis by Vanessa Walsh. We acknowledge funding from the NSDNR Wildlife Division and the Natural Sciences and Engineering Research Council of Canada (NSERC) through Discovery grants to MZ and HGB. We are thankful for the suggestions of two anonymous reviewers, which considerably improved the manuscript. REFERENCES ALBAREDE, F. 2003. Geochemistry: An In- troduction. 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