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Consumption of desert gourds by collared peccary suggests the fruit is not an ecological anachronism.

The desert gourd (Cucurbita foetidissima) is a recumbent, multi-stemmed vine extending 6 m or more with a large perennial root, occurring from Missouri west to Nebraska and south to southern California, northern Mexico, and western Texas (Correll and Johnston, 1979). The indehiscent fruit consists of a fibrous pulp encased within a tough exocarp, contains small seeds (ca. 10 mm in length), has a strong odor, and turns lemon-yellow upon ripening (Correll and Johnston, 1979). Few animals are known to consume the fruit, presumably because the pulp is rich in extremely bitter cucurbitans (Nwokolo, 1996), which can cause nausea, extreme abdominal cramps, vomiting, and diarrhea if ingested (Tweit, 1995). Consequently, it remains unclear how the seeds of desert gourd are dispersed (Barlow, 2000). Nonnative horses and burros (Equidae) occasionally consume fruits when other forage is unavailable (Barlow, 2000). Pocket gophers (Geomyidae) hoard fruits in underground larders (Barlow, 2000), but larder-hoarding tends to concentrate rather than disperse seeds (Hulme, 2002). Desert box turtles (Terrapene ornata) reportedly consume fruits (Ernst and Lovich, 2009), although their role as seed-dispersal agents has not been investigated. Nabhan (1987) speculates that dried fruits of C. foetidissima are dispersed by flashfloods; however, Barlow (2000) contends buoyancy of fruit is probably not an adaptation for dispersal of seeds. Even when dried, the large fruits are unlikely to be dispersed by wind. Because C. foetidissima appears to lack effective dispersal agents and attributes of fruit are consistent with the megafaunal dispersal syndrome of Janzen and Martin (1982), Barlow (2000) considers the fruit to be an extreme ecological anachronism (a trait that evolved in response to selective pressures that have since disappeared, without a corresponding change in the trait; Janzen and Martin, 1982) wholly dependent on now-extinct Pleistocene megafauna for dispersal.

We report the consumption of fruit of C. foetidissima by collared peccary (Pecari tajacu), speculate on their potential to disperse seeds, and question previous assumptions regarding the role extinct megafauna played in this mutualism. Our investigation was conducted near Alpine (Brewster County), in the Trans-Pecos region of western Texas. Alpine (30[degrees]21'N, 103[degrees]39'W; elevation of ca.1,370 m) is surrounded by desert grassland with significant areas of encroachment by shrub (Powell, 1998; McCleery et al., 2005). During October 2009 and 2010, we collected mature fruits of C. foetidissima from scattered sites in Brewster and Presidio counties, Texas. Fruits were placed in a wire basket shortly after collection and refrigerated until used in feeding trials. We conducted feeding trials at a wildlife-feeding station on the outskirts of Alpine where ca. 2 L of whole corn was provided daily to attract collared peccary and mule deer (Odocoileus hemionus) for recreational viewing. The feeding station was located in an open area characterized by exposed soil and sparse, closely cropped grass. Feeding trials were conducted from 15 November-16 December 2009, 7 November-17 December 2010, and 24January-22 February 2011. To our knowledge, these were years of typical availability of food. Furthermore, gourds ripen during September-October and remain available to potential consumers throughout the late fall and winter, a period coinciding with our feeding trials. During each feeding trial, gourds were placed on the ground about 1 m from where corn was dispensed to maximize the likelihood that ungulates feeding on the corn would encounter the gourds. Four fruits were used in each trial except in 2009 when the final trial consisted of a single remaining fruit. Fruits were usually placed at the station 1.0-1.5 h before dusk. The feeding station was monitored daily, and any partially eaten fruits were noted and removed. We also searched the area (ca. 0.5 ha) surrounding the feeding station to detect partially eaten fruit, fruit that may have been transported away from the station but not consumed by ungulates, and scats from peccary. Activity of wildlife was monitored with a Wildview Xtreme (STC-TGL2M) Game Camera (Wildview, Grand Prairie, Texas) set to take digital photographs at 1-min intervals (the smallest interval-setting available). Photographs were downloaded the following day, and the camera was replaced at the feeding station before dusk. Budgetary constraints precluded the use of video recorders with nocturnal capabilities to monitor the feeding station. We also monitored (three times weekly; October-January) vines and fruit of C. foetidissima on the Sul Ross State University Ranch immediately adjacent to the main campus in Alpine for evidence of feeding activity of wildlife. Game-cameras were not placed at this site because of concerns about security; instead, we used tracks and other signs (e.g., missing and partially eaten fruits) to monitor feeding activity of wildlife. The Sul Ross State University Ranch is located ca. 4.0 km NE of the feeding station.

We placed 21 and 32 fruits of C. foetidissima at the feeding station during 2009 and 2010-2011, respectively, all of which were removed by wildlife. Fruits were removed within 1-3 nights (95.2% removed within 2 nights) in 2009 and 1-13 nights (71.8% removed within 2 nights) in 2010-2011. Four (19.0%) partially eaten fruits were recovered at the feeding station in 2009, and two (6.2%) in 2010-2011. In five cases, >50% of the fruit had been consumed, while, in the remaining case, ca. 75% of the fruit remained uneaten. Fragments of exocarp were found at the feeding station on numerous occasions during both periods of the study. Other than a few scattered grains, 100% of the whole corn was consumed by ungulates during each night of the feeding trials. Collared peccary and mule deer were regularly photographed at the feeding station, although we attribute all instances of removal of fruit to the former. The camera failed to record most feeding events; instead, we usually obtained a series of photographs where fruits were initially visible together with feeding peccaries (group of 1-5) but absent in subsequent photographs which show only peccaries. Because the camera was set to photograph at intervals of 1 min and was constantly triggered by moving peccaries, relatively brief feeding events probably escaped detection. In other cases, peccaries standing in front of the camera obscured feeding events. Despite the difficulty of capturing feeding events on camera, we nonetheless obtained photorecords of peccaries consuming fruit on six occasions. Importantly, fruits were never removed on nights when only mule deer were photographed, and numerous photorecords indicated the deer ignored the fruits. We found nothing to suggest fruits had been removed from the feeding station but not eaten. Searches of the area surrounding the feeding station yielded only partially eaten fruits. We found nothing to indicate collared peccary removed fruits from the feeder without consuming them. Because sparse grass-cover surrounded the feeder, any such fruits would likely have been detected. No scat from peccary was found in the vicinity of the feeding station.

In addition to feeding trials, opportunistic monitoring of patches of gourd at the Sul Ross State University Ranch provided further evidence of consumption of fruit by collared peccary. We found a partially eaten fruit (<50% remaining) and noted the removal of five others from a patch of gourds over a period of 10 days in mid-October 2009. Tracks in the immediate vicinity indicated these fruits were consumed by a group of peccaries. Tracks of peccary were readily distinguished from those of mule deer and cattle (Bos), which also occur on the property, on the basis of shape and size (Murie and Elbroch, 2005). Similarly, nine fruits were removed from a patch of gourds in the same area during late October 2010; however, the surrounding substrate was unsuitable for capturing tracks. Interestingly, a single fruit was found with a small hole (diameter of ca. 4 cm) through which the contents (pulp and seeds) had been extracted. Evidence of gnawing around the periphery of the hole indicated the contents were extracted by a rodent, possibly Neotoma micropus which is common at the site. To our knowledge, this is the first report of predation on seed of C. foetidissima and suggests rodents may consume hoarded gourds rather than disperse the seeds.

Collared peccary are highly opportunistic herbivores that consume the fruit, foliage, bulbs, rhizomes, roots, and tubers from a diverse array of grasses, forbs, succulents, and woody plants (Jennings and Harris, 1953; Knipe, 1957; Leopold, 1959; Neal, 1959; Eddy, 1961; Everitt et al., 1981; Bissonette, 1982; Corn and Warren, 1985; Sowls, 1997; Beck, 2005); however, our observations constitute the first report of fruit of C. foetidissima in the diet. Collared peccary also reportedly consume the roots of C. foetidissima and C. digitata (Eddy, 1961), suggesting the presence of bitter cucurbitans does not deter feeding on gourds. Consumption of gourds is not wholly unexpected because collard peccaries are known to eat fruits from a wide morphological and taxonomic spectrum, including a number of species containing bitter compounds (Beck, 2005).

Whether or not collared peccary are effective vectors for dispersal of seeds of C. foetidissima remains to be determined. Seeds ingested by peccaries can be destroyed by their strong masticating apparatus or chemically digested during pregastric fermentation (Langer, 1978; Kiltie, 1982; Beck, 2005). However, small seeds ([less than or equal to] 1.0 cm in length) such as those of C. foetidissima are likely to escape crushing during mastication and often are resistant to chemical breakdown (Beck, 2005). Furthermore, although seeds of gourds were not tested, tests of germination of other small seeds recovered from feces from peccary confirm that many species remain viable subsequent to passage through the gastrointestinal tract (Beck, 2005). Because seeds remain in the digestive tract for [less than or equal to] 5 days (Gonzalez-Espinosa and Quintana-Ascencio, 1986) and home ranges are extensive (165-247 ha in our area; Green et al., 2001) with daily movements [less than or equal to] 10 km reported, collared peccaries can transport seeds over long distances and generate extensive seed-shadows (spatial distribution of dispersed seeds around their source; Beck, 2005). For these reasons, we suggest collared peccaries be considered as potentially effective dispersal vectors of seeds of C. foetidissima but caution this can only be verified through germination-trials of seeds recovered from feces (e.g., Liu et al., 2004; Beck, 2005). Indeed, much remains to be learned about the ecological relationship between C. foetidissima and collared peccary. Because studying this mutualism in wild collared peccary is difficult, feeding trials of captive individuals would seem a worthwhile avenue for future research. Such ex-situ studies offer a means to address many questions that might not otherwise be answered, including fate of seeds, rates of passage through the gastrointestinal tract, and other components of the effectiveness of dispersers (Schupp, 1993; Liu et al., 2004).

In light of our observations in the field, the contention that fruit of C. foetidissima is an extreme anachronism warrants reconsideration. Ernst and Lovich (2009) reported one potential disperser (Terrapene ornata), we identified another (collared peccary), and others are likely given the diffuse rather than specialized nature of many mutualisms of seed dispersal (Herrera, 1985). Of course, our observations by no means preclude dispersal by extinct megafauna. Seeds of Cucurbita pepo found among digesta of mastodon (Mammut americanum) suggest extinct proboscideans as likely dispersal agents (Newsom et al., 1993). Additionally, the recumbent form of growth of C. foetidissima and terrestrial (or nearly so) presentation of ripe fruit may be an adaptation for dispersal by extinct giant tortoises (Geochelone), and the fact that extant equids occasionally consume gourds (Barlow, 2000) suggests extinct species might have done likewise. Finally, our findings underscore the need for careful observations in the field to explore alternatives to dispersal by extinct megafauna and highlight the risk of assuming potential dispersal agents are absent from contemporary ecosystems (Howe, 1985).

We are grateful to L. Epps, L. A. Harveson, M. Thompson, and H. Beck for providing literature, J. M. Williams and L. Medlock for assistance with maintaining the feeding station and wildlife-camera, and P. Charruau for translating our abstract into Spanish. Support for SGP and PRM was provided by the Department of Biology at Sul Ross State University, Alpine, Texas. The findings and conclusions in this article are those of the authors and do not necessarily represent the views of the United States Fish and Wildlife Service.

LITERATURE CITED

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Submitted 2 July 2012. Acceptance recommended by Associate Editor Jennifer K. Frey 3 May 2013.

STEVEN G. PLATT, PATRICIA R. MANNING, AND THOMAS R. RAINWATER *

Department of Biology, Box C-64, Sul Ross State University, Alpine, TX 79832 (SGP, PRM)

United States Fish and Wildlife Service, Ecological Services Field Office, 176 Croghan Road, Suite 200, Charleston, SC 29407 (TRR)

Present address of SGP: Wildlife Conservation Society, Myanmar Program, Office Block C-1, Aye Yeik Mon 1st Street, Hlaing Township, Yangon, Myanmar

* Correspondent: trrainwater@gmail.com
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Title Annotation:NOTES
Author:Platt, Steven G.; Manning, Patricia R.; Rainwater, Thomas R.
Publication:Southwestern Naturalist
Article Type:Report
Geographic Code:1USA
Date:Mar 1, 2014
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