Michelle P. Scott, James F. A. Traniello, and Isabelle A. Fetherston.
Competition for prey between ants and burying beetles (Nicrophorus spp.): differences between northern and southern temperature sites.
Psyche 94:325-332, 1987.

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COMPETITION FOR PREY BETWEEN ANTS
AND BURYING BEETLES (NICROPHOR US SPP):
DIFFERENCES BETWEEN NORTHERN AND SOUTHERN TEMPERATE SITES.
Department of Biology, Boston University, Boston, Massachusetts 02215
Burying beetles (Silphidae: Nicrophorus) utilize small vertebrate carcasses which can be quickly buried or rolled down a hole and concealed. Because carrion is also used by other invertebrates and vertebrates, burying beetles may be in competition with species of a wide variety of taxa for access to carcasses. For example, calli- phorid flies are often first to oviposit on carrion and if the eggs are not detected and destroyed by Nicrophorus the carcass may be con- sumed by developing fly larvae, causing the beetles to abandon the resource.
One aspect of resource competition in Nicrophorus that has not been examined concerns interactions between burying beetles and ants (Arnett 1946). Ants are abundant, omnivorous scavengers in many habitats; ant colony size is often large and many species have swift recruitment systems that would allow them to occupy and defend small vertebrate prey. Ant species diversity and abundance are known to follow a latitudinal gradient (Kusnezov 1957, Wilson 1971, Jeanne 1979), and therefore the predatory or scavenging hab- its of ants may exert different effects on the ability of northern and southern temperate Nicrophorus species to control small vertebrate carrion. In this paper we report on the results of a study examining competitive interactions between burying beetles and ants at north- ern and southern sites in North America. The natural history of burying beetles (Nicrophorus spp.) and their ecological relationships have been well described (Pukowski *Revised manuscript received by the editor September 10, 1987. 325




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326 Psyche [vo~. 94
1933, Milne and Milne 1976, Anderson 1982, Wilson 1983, Wilson et al. 1984, Wilson and Knollenberg 1984, Wilson and Fudge 1984). Males and females are attracted to carrion, and intrasexual compe- tition occurs within each sex until usually only one male and female remain. The pair may then move the corpse; both sexes dig beneath to bury it, remove the fur or feathers of the carcass, and roll it into a ball treated by both male and female with anal and oral secretions. Following burial, the female's ovaries rapidly complete develop- ment (Scott and Traniello 1987) and she lays approximately thirty eggs in the soil nearby which hatch into altricial larvae that are fed regurgitated food by both parents. The larvae are soon capable of feeding from the corpse directly, but may also receive food from their parents throughout development. About two weeks after bur- ial, the larvae leave the burial chamber and pupate in the soil nearby. Usually, at least one parent remains with the brood until larval dispersal.
Ant and burying beetle competition was studied in a mixed hard- wood (maple/ birch/ beech) and softwood (pine/ hemlock/ spruce) forest at Jaffrey, New Hampshire (Cheshire County) and in a pineloak forest and two field sites at Wimauma, Florida (Hills- borough County). Nicrophorus sayi, N. orbicollis, N. defodiens, and N. tomentosus are common at the northern site, and N. orbicollis and N. carolinus were trapped in Florida. In order to study abundance and diversity of ants and burying beetles, a transect of 10-25 pitfall traps (0.95 liter jars) located 10 m apart was set out on each site. In New Hampshire these were baited with aged beef kidney and in Florida with previously frozen whole chicks (Gallus gallus) which did not dry out in the heat and were more effective in attracting all invertebrates. Pitfall traps were censused after 24 h. To examine competition between ants and beetles for the utilization of small vertebrate carrion, previously frozen mice (Mus musculus), 8-60 g, or chicks, 45-55 g, were placed over 0.95 liter jars or 1 1.4 liter pots filled with potting soil and sunk into the ground at 25-m intervals. These traps were censused every 24 h and the ultimate fate of each carcass (buried by beetles, overrun by ants until the carcass was consumed or was no longer attractive, removed by vertebrates, or utilized primarily by flies) was recorded. The traps containing carcasses buried by beetles were retained and adults leaving the brood chamber, and either eclosing flies or teneral



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19871 Scott et al.-Ants and burying beetles 32Ìö beetles were captured. Studies were conducted June-August 1984- 1985 in New Hampshire and May-July 1986 in Florida. RESULTS
Burying beetles were readily caught in pitfall traps at both Ioca- tions. In New Hampshire, 662 beetles of all four above-tnentionesd common species were trapped in 525 trap-nights in 1984 and 4 5 7 beetles were trapped in 525 trap-nights in 1985. Ants (Camponott-^ts novaboracensis, Acanthomyops sp. and Aphaenogaster sp p) were found in less than 2% of the pitfall traps and always in low numbers (less than 10). At the southern site 441 beetles were trapped in 7-4 trap-nights. Ninety-five percent of these were N. carolmus whic- 3-1 were trapped in equal numbers in the forest and in the field. J^^. orbicollis were captured primarily in the forest. Ant/ burying beetle interactions were related to habitat also, reflecting the prirnaril, y open-field distribution of the imported fire ant Solenopsis invicta. In the forest S. invicta was found in 33% of the pitfalls and other amt species in 9% (N = 360); in the field 6 1% of the pitfalls were occm- pied by fire ants and 6% by other ant species (N = 434). Infarmatio n on ant abundance from the pitfall traps at the two study sites sirrt- ilarly indicates a greater potential for ant interference at the Florid a site. When ants were present in pitfalls, 94% of traps contained more than approximately 100 workers. Other ant species (Camponotus abdominalis floridanus, Crematogaster clam) were found in pit fall traps in small numbers (less than 10). Pheidde dentata, P. momens* Crematogaster ashmeadi and Conomyrma sp. were found at baits i m the same habitat but not in the pitfall traps. There were striking differences between sites in New Hampshire and Florida in the percentage of mice or chicks available that were successfully buried by Nicrophoiw spp. (42% vs 10%, N = 172 and 48, respectively, t, = 4.70, P < 0.001, angular transformation tes- -t for the equality of two percentages). In New Hampshire, N. orbicoy- Us was the dominant species and accounted for 55% of the carrion buried. In Florida, only N. carolinus successfully buried prey item: experimentally offered. Only 12% of all prey were ultimately utilized by ants at the northern site. Generally, only a few ants were presen -it. at a time with the exception of two or three small prey which were completely overrun with Acanthomyops. In contrast, significantly more (77%) of the prey at the southern site were utilized by ants



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328 Psyche [Vol. 94
primarily Solenopsis (ts = 8.79, P < 0.001). Other ant species col- lected in pitfall traps were not observed on these prey placed on the surface, perhaps due to displacement by fire ants. Flies were more successful in utilizing prey in New Hampshire (is = 7.23, P< 0.001) perhaps also due to displacement by fire ants in Florida. At both sites, prey size affected its ultimate utilization. In New Hampshire, ants were significantly more successful at utilizing small prey (< 30 g, ts = 5.34, P < 0.001) and flies were significantly more successful utilizing large prey (ts = 5.45, P < 0.001). In Florida, beetles were less successful in burying small prey (ts = 2.30, P < 0.02) but ants were equally successful with large or small prey (is = 0.96, P = 0.33; Table 1).
The wide range of feeding habits of ants produce considerable dietary overlap with members of other, unrelated taxa utilizing the same resources (see for example Brown and Davidson 1976). Because many ant species are opportunistic and scavenge for a wide variety of sizes and types of animal prey, it is not unusual that carrion may be used as a food source when available. Such a large, concentrated resource will induce an extraordinary recruitment response from a colony, perhaps exhausting all foragers within the nest. Although the sensitive chemoreceptors of Nicrophorus permit them to locate carrion over long distances, the high density of forag- ers of ant species with well-developed trail communication and chemical or aggressive defense of resources may bring burying bee- tles and ants into competition for small vertebrate carcasses. Even if prey are first found by Nicrophorus, the time during which intra- sexual competition occurs and burial is completed could increase the time period in which the carcass might be located by ants and thus increase the probability that they would displace the beetles. In the present study the lack of success of Florida Nicrophorus on carcasses was apparently due to interference from fire ants rather than to a lack of beetles in the study area because 416 N. carolinus were collected from pitfall traps but only five prey (N = 48) were buried. The nocturnal activity of some Nicrophorus species might favor early detection of carcasses and successful utilization, but this advantage would depend upon the temporal pattern of vertebrate mortality. Carcasses could also be lost to ants following burial, as



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Scott et a[.-Ants and burying beetles
Table I.
Ultimate use of prey of different sizes in New Hampshire and Flori- a. Prey unaccounted for in the table (I?%, t2%, 33'75% and 5% for smdl and large p r v y , NH and FL, respectively) disappeared and were presumed to have been taken t>y vertebrates. N = sample size.
Prey size
Use by:
(grams) N beetles ants flies
New Hampshire 8-29 69 45% 28% 10%
30-60 103 41% 2% 46%
Florida 20-25 12 0 67% 0
45-55 36 14% 81% 0
many species have subterranean as well as epigaeic foraging habit :. In addition to loss to ants, Nicrophorw will abandon carcass-s that are infested with fly larvae. The mutualism between buryi-g beetles and Poecititu mites that are predators of fly eggs appears 6 a have evolved in the context of reducing competition with dipera-s (Wilson 1983). Also, the cooperative burial shown by the dium-1 Nicrophorus tomentoms may function in accelerating carcass m i - cealment, thereby reducing prey availability to flies during t l e warmer periods of the day when fly activity is greater (unpublishe 4 data). We observed no behaviors in Nicrophorus that could haÌÔiÌÔ> interpreted as specific to ant/beetle competition, although the-aiÌÔÌÔE coordinated carcass movement (Pukowski 1933, Milne and M i l i e 1976) could have the effect of decreasing the chance of ant utilize- tion. Moving the carcass to a site suitable for burial might i n v o l ~ s selection of appropriate soil conditions and lower ant abundant- - The few direct interactions we observed between ant and buryim A- beetles were characterized in New Hampshire (between one beetlÌ - and less than 10 ants) by indifference or removal of the ant w h i c m had come in contact with the beetle's leg. In Florida, however- - Nicrophorus avoided carcasses occupied by ants. There are 85 species of Nicrophorus worldwide, most bein- European and Asian in distribution, and there is a decrease in sp- - cies diversity at southern latitudes in both the Old and New Worl<- (Peck and Anderson 1985). In the New World, fifteen species occix- x in the United States and Canada, nine in Latin America, three 3 which are endemic to South America and two endemic to Centr-3 America (Anderson and Peck 1985). The biogeography of silphid ; in general indicates that they we less prominent members of tropic-



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330 Psyche [vo~. 94
carrion-feeding insect guilds than in temperate regions (Carnaby 1974, Jirh and Cartin 1981). It has been suggested that their lower abundance in the tropics is due to the increased loss of carrion to bacteria, fly larvae, carrion-scavenging vertebrates and ants (Arnett 1946, Peck and Anderson 1985). It would be tempting to assume that the inverse correlation between ant and burying beetle species diversity is a causal factor in the distribution of silphids. However, our limited study of competition between ants and burying beetles allows us to conclude only that ants may exert at least a strong, local effect on the ability of burying beetles to secure carrion. This effect does not appear dependent only on interactions with the imported species Solenopsis invicta; the native S. geminata also dominates carrion placed out at other sites in Florida (Lloyd Davis, pers. comm.). Although there is a difference in ant species diversity between the two sites in our study (approximately twelve species total in New Hampshire and sixteen to thirty in Florida; Jeanne 1976, Calabi 1986, Trager, pers. comm., Traniello, pers. obs.), we cannot conclude that there is a direct cause-and-effect relationship between ant diversity and the ability of ants to control prey poten- tially available to burying beetles. In fact Jeanne's (1979) data show that predation rate by ants was higher on the ground than on vege- tation although ant species diversity was higher in the latter micro- habitat. Although very little is known about the use of small vertebrate carrion in the tropics, such resources may be exploited by ants, and the presence of only a few dominant ground species may reduce burying beetle reproductive success. Given the information available on the patterns of distribution and abundance of ants, it can be inferred that carrion may be approached more frequently by ants in the tropics than in the temperate zone. A relatively small number of omnivorous genera having species with large colony size and rapid recruitment communication may effectively restrict the use of carrion by burying beetles, perhaps producing patterns in the tropics similar to what we have described in Florida. In New Hamp- shire and Florida the relative importance of ants in Nicrophorus ecology seems dramatically different, but the relative importance of the distribution of ants, flies, and microbes in the biology of burying beetles remains to be determined.




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19871 Scott et al.-Ants and burying beetles 331 By sampling the diversity and abundance of burying beetles and ant species utilizing small vertebrate carcasses with pitfall and burial traps and recording the success of Nicrophorus spp. in securing carrion for reproduction, we found that ant interference was more prevalent in a population in central Florida than in southern New Hampshire. Carrion placed along transects in central Florida was occupied by the imported fire ant Solenopsis invicta, and although burying beetles were abundant in the area, few prey were success- fully utilized. It is concluded that some ground-dwelling ant species may have a significant local impact on burying beetle reproductive ecology.
We thank Dr. James Trager for identifying ants at the Florida site and Dr. Lloyd Davis for comments on the manuscript. Funds for this research were provided by Grant GRS 805 BI from the Gradu- ate School of Boston University, by a grant from the Boston Uni- versity chapter of Sigma Xi to I.F., and by NSF grant BNS 82 16702 to J.F.A.T., and by a Science Scholars Fellowship from the Mary Ingraham Bunting Institute of Radcliffe College sponsored by the Office of Naval Research to M.P.S.
ANDERSON, R. S. 1982. Resource partitioning in the carrion beetle (Coleoptera: Silphidae) fauna of southern Ontario: ecological and evolutionary considera- tions. Can. J. Zool. 60: 1314-1325.
ANDERSON, R. S. AND S. B. PECK. 1985. The Silphidae and Agyrtidae of Canada and Alaska. The Insects and Arachnids of Canada, Part 14. Agriculture, Canada.
ARNETT, R. H., JR.
1946. Coleoptera notes I: Silphidae. Can. Ent. 78: 131-134. BROWN, J. H. AND D. DAVIDSON. 1976. Competition between seed-eating rodents and ants in desert ecosystems. Science 196: 880-882. CALABI, P.
1986. Division of labor in the ant Pheidole dentata: the role of colony demography and behavioral flexibility. Ph.D. thesis, Boston University. CORNABY, B. W. 1974. Carrion reduction by animals in contrasting tropical habi- tats. Biotropica 6: 51-63.




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Psyche
[Vol. 94
JEANNE, R. L. 1979. A latitudinal gradient in rates of ant predation. Ecology 60: 121 1-1224.
JIR~N, F. F. AND V. M. CARTIN. 1981. Insect succession in the decomposition of a mammal in Costa Rica. J. N. Y. Ent. Soc. 89: 158- 165. KUSNEZOV, N.
1957. Numbers of species of ants in faunae of different latitudes. Evolution 11: 298-299.
MILNE, L. J. AND M. MILNE. 1976. The social behavior of burying beetles. Sci. Am. 235: 84-89.
PECK, S. B. AND R. S. ANDERSON. 1985. Taxonomy, phylogeny, and biogeo- graphy of the carrion beetles of Latin America (Coleoptera: Silphidae). Quaest. Ent. 21: 247-317.
PUKOWSKI, E. 1933. ~kologische untersuchungen an Necrophorus F. Z. Morph. oekol. 27: 518-586.
SCOTT, M. P. AND J. F. A. TRANIELLO.
1987.
Behavioural cues trigger rapid ovar-
ian development in the burying beetle Nicrophorus tomentosus. J. Insect. Phy- siol., 33: 693-696.
WILSON, D. S. 1983. The effect of population structure on the evolution of mutu- alism: a field test involving burying beetles and their phoretic mites. Am. Nat. 121: 851-870.
WILSON, D. S. AND J. FUDGE.
1984. Burying beetles: intraspecific interactions and reproductive success in the field. Ecol. Ent. 9: 195-203. WILSON, D. S. AND W. G. KNOLLENBERG. 1984. Food discrimination and ovarian development in burying beetles (Coleoptera: Silphidae: Nicrophorus). Ann. Ent. Soc. Am. 77: 165-170.
WILSON, D. S., W. G. KNOLLENBERG AND J. FUDGE. 1984. Species packing and
temperature dependent competition among burying beetles (Silphidae, Nicro- phorus). Ecol. Ent. 9: 205-216.
WILSON, E. 0. 1971. The Insect Societies. Belknap Press, Cambridge.



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