Can golf course ponds be a safe haven for amphibians?
Although a golf course will never replace unfettered nature, it is a green space that can preserve some of the local biodiversity of an area. Golf courses can benefit amphibians, such as frogs and salamanders, which are experiencing declines worldwide due to habitat loss, disease, chemical contaminants and exotic species (7).
Pond-breeding amphibians start their lives in water and metamorphose to live on land until they return to ponds to reproduce, making them critical players in aquatic and terrestrial ecosystems. Because designers frequently plan wetlands on golf courses, these courses have the potential to attract local amphibians. Amphibian communities are most diverse in habitats with temporary ponds because these habitats are nutrient-rich and lack predatory fish.
Because frogs and toads feed on algae as tadpoles, they help clear pond water and reduce the likelihood of floating algal mats. Salamander larvae feed on larval mosquitoes in the water, reducing the number of flying pests. As adults, all amphibians eat insects and are voracious predators, reducing the number of nuisance species.
Pesticides combat pest species, but they have financial and time costs, not to mention environmental costs. Although they can eliminate algae or mosquito larvae for one season, managers may need to spray yearly or multiple times yearly. Pesticides can also reduce the abundance of natural invertebrate predators of insect pests, which may require greater chemical management.
Additionally, many courses use herbivorous fish to control algae or mosquitofish (Gambusia spp.) to prey upon mosquitoes. While stocking ponds with fish may be a one-time investment, it will likely exclude the potential for diverse amphibian communities.
For instance, we found that the presence of fish, regardless of their diet, can negatively influence amphibians. By providing suitable habitat for amphibians, they will often arrive independently and can provide pest control over time without any significant investment from course managers (1).
If using native amphibians as biocontrol agents sounds great, then what does it take to attract diverse amphibians to your course? When golf courses are relatively close to natural habitats, it can be as simple as “build it, and they will come.”
Most of the courses we have visited appear to have some amphibians using those sites. The amphibian populations on a golf course can be self-sustaining, or population sinks that attract local amphibians from nearby sites which fail to produce offspring.
In the past, our lab has investigated if golf courses can provide suitable habitats for self-sustaining amphibian communities. Initially, we conducted studies in Missouri at two golf courses and two reference ponds using enclosures containing larvae of three local amphibian species in the presence or absence of overwintered bullfrog (Rana catesbeiana) tadpoles (2), a common competitor found in golf course ponds (6).
We thought golf courses would be poor habitats for amphibians because of fertilizer and pesticide use, which could subsequently enter aquatic environments where amphibians develop. However, we were surprised that amphibians in golf course enclosures without bullfrog tadpoles did as well or better than those at natural reference sites (2).
Golf course ponds that mimic the natural hydrology of temporary ponds by drying in late summer to early fall can help support native amphibian communities by excluding some of their competitors and predators (2). Pond drying reduces the presence of amphibian competitors like bullfrogs or green frogs, which typically overwinter in ponds and reach large sizes before metamorphosing the following spring.
The aquatic life stage is only one part of the equation for pond-breeding amphibians. Most amphibians spend a few weeks or months in the pond and spend the rest of their life on land, which may last one year to a decade or more. If golf courses can serve as suitable habitats for amphibians, as our study in Missouri suggested, then having adequate terrestrial habitat is also essential. But what is suitable terrestrial habitat, and how likely is it to coincide with habitats on golf courses?
Many amphibians are forest-associated, like spotted salamanders (Ambystoma maculatum) and American toads (Bufo americanus). Many forest-associated amphibians could benefit from golf course ponds located nearby. Other amphibians, like cricket frogs (Acris crepitans) or northern leopard frogs (Rana pipiens), are grassland-associated. Leopard frogs will roam terrestrial habitats after laying their eggs in ponds, while cricket frogs stay near ponds during warmer months.
Golf courses seem especially suited to facilitating species that use grassland ponds and spend much of the year near the pond. However, golf course managers should not have to study the natural history of local species to determine which habitat characteristics may be most important because many amphibian species can benefit from leaving areas that are out-of-play more natural by not mowing or directly managing them. This type of management not only saves money but can also help amphibians persist at a golf course.
One of the sites where we worked placed signs in unmanaged areas like “Butterfly Wildlife Area” to highlight to golfers the advantages of these spaces. Studies of amphibians in natural systems suggest that amphibians use approximately 500 to 1,000 feet around a pond (8); however, they may be able to use less area, particularly if habitats present fulfill their needs.
A central management practice we associate with golf courses is mowing grass, which is essential for putting greens and areas in play. On some courses, up to 70 percent of the golf course may be out of play and often (or can be) left unmown or less managed, which could be particularly useful to amphibians when these areas are near ponds.
Unmown, grassy areas provide habitat for many beneficial insects, including butterflies, and also critical habitat for amphibians. For grassland species like cricket frogs, unmown fields offer a refuge from the desiccation of the sun and wind, a place to hide from predators, a pathway to disperse and a source for insects on which they feed.
To examine the role of habitat management on golf courses in Ohio, we worked with three courses that each had at least two ponds, one of which the managers left with an unmown grassy area or “buffer zone” of at least three feet and the other that they mowed up to the edge (4). We put tadpoles of green frogs and cricket frogs in separate enclosures in these ponds and reared them for a few months until cricket frogs metamorphosed and green frogs grew into larger tadpoles (Below).
Cricket frogs are a grassland-associated species that are declining in parts of their range, so if green spaces like golf courses could benefit this frog, it may help maintain populations in some areas. Green frogs, in contrast, are doing well throughout their range and are associated with humans; therefore, they may not be as sensitive to habitat manipulation.
Like our Missouri study, we found that tadpoles survived well in golf course ponds (4), suggesting that aquatic habitats on golf courses are sufficient for many amphibian species. We also found that the presence of the buffer zone made a difference for both cricket frogs and green frogs.
The buffer zone increased survival for cricket frogs, suggesting that it filtered out pesticides or fertilizers applied on the golf course. In contrast, green frogs did better without a buffer zone because green frogs are more tolerant of contaminants than cricket frogs (1).
Our results suggest that even partial buffer zones may benefit many species. The management of buffer zones does not have to be an all-or-nothing decision. Because cricket frogs are a more sensitive species, our study suggests that buffer zones could benefit the larval development of these species and be a useful management tool for maintaining local amphibian diversity at golf course ponds (4).
We also examined how buffer zones influenced cricket frog survival in the terrestrial environment. We marked and released all of the cricket frogs reared in our enclosures in golf course ponds and returned to the course in the spring to search for them. However, we found none of the cricket frogs that had been marked (4), which could result because the terrestrial environment on golf courses was insufficient for survival, because individuals moved to other locations away from golf course ponds or because we did not release enough individuals to ensure the likelihood of recapture.
To understand how characteristics of terrestrial habitats could influence juvenile and adult cricket frogs, we also studied cricket frog preferences for mown versus unmown grass in enclosures where they had choices (4). We also released powdered cricket frogs (below) on golf courses to examine how mown and unmown habitat influenced their movement (5).
First, we found that cricket frogs favored unmown grass over mown grass (4). Subsequent studies indicated that cricket frogs prefer habitats with greater moisture afforded by unmown grass. Furthermore, we also found that cricket frogs released on golf courses in unmown grass traveled further than those released on mown grass and that those released in unmown grass were best able to orient toward a pond (5).
These studies suggest that unmown grass provides a preferred habitat for cricket frogs and could increase their ability to find ponds efficiently. Because unmown grass harbors more food resources, maintains moisture and provides a place to hide from predators, unmown grass is likely helpful for amphibians who would use ponds on golf courses.
Ponds on courses result in survival similar to or greater than natural reference ponds, and unmown buffer zones may benefit the terrestrial survival of many species by providing refuge and food. However, our research suggests not all aquatic and terrestrial habitats are equal. The more closely habitats mimic natural systems, the more likely golf course managers will reap the free rewards of nature.
Aquatic habitats without fish that dry down yearly to every other year during the late summer or early fall are most likely to support diverse amphibian communities. Harboring diverse communities means protecting more local amphibians and reaping the ecosystem services of amphibians throughout the year.
Unmown grassy edges around ponds help improve the water quality of golf course ponds by filtering out fertilizers and pesticides before reaching the water. Buffer zones around ponds can also provide essential habitat for amphibians during their terrestrial life while they avoid desiccation, hide from predators and search for food.
Looking to nature as a guide for management can serve as a means for keeping all of the needed habitat pieces (3) and restoring ecosystem services in managed areas. With more than half of the world’s wetlands lost (9), habitat destruction is a significant issue for aquatic-associated species. When green spaces like golf courses can help mitigate the effects of habitat destruction to some extent, everyone wins.
Adapted by Michael Kenna, Ph.D. from Michelle D. Boone, Ph.D., and Holly J. Puglis, Ph.D. 2013. Keeping all the Pieces: Restoring Natural Processes for Easier Golf Course Management. USGA Turfgrass and Environmental Research Online. 12(4):1-5.
For additional information, contact Michelle Boone, Ph.D., Department of Biology, Miami University, at boonemd@miamiOH.edu.
Research Takeaways
- Amphibian communities are most diverse in habitats with temporary ponds in habitats with temporary ponds because these habitats are nutrient-rich and lack fish, predators that frequently eliminate most species of amphibians
- Cricket frog (Acris crepitans) and green frog (rana clamitans) survival was reduced dramatically when reared in experimental ponds with grass carp (Ctenopharyngodon idealla) or predatory bluegill sunfish (Lepomis macrochirus)
- For grassland species like cricket frogs, unmown fieldls provide a refuge from the desiccation of the sun and wind, a place to hide from predators a pathway to disperse and a source for insects on which they prolifically feed.
- Buffer zones of three feet or more around ponds increased the survival of cricket frogs.
References
- 1. Ade, C. M., M. D. Boone, and H.J. Puglis. 2010. Effects of an insecticide and potential predators on green frogs and northern cricket frogs. Journal of Herpetology 44:591-600.
- 2. Boone, M. D., R. D. Semlitsch, and C. Mosby. 2008. Suitability of golf course ponds for amphibian metamorphosis when bullfrogs are removed. Conservation Biology 22:172-179.
- 3. Gibbons, W. 1993. Keeping All the Pieces: Perspectives on Natural History and the Environment. Smithsonian Institute. Washington, D.C.
- 4. Puglis, H.J., and M. D. Boone. 2012. Effects of terrestrial buffer zones on amphibians on golf courses. PLoS One 7:e39590. Doi:10.1371/ journal.pone.0039590.
- 5. Ramirez, E. A., H.J. Puglis, A. Ritzenthaler, and M. D. Boone. 2012. Terrestrial movements and habitat preferences of male cricket frogs on a golf course. Copeia 2012:191-196.
- 6. Scott, D. E., B. S. Metts, and J. W. Gibbons. 2008. Enhancing amphibian biodiversity on golf courses with seasonal wetlands. Pages 285-292 in Urban Herpetology, Jung, R. E., and J. C. Mitchell (eds.) Herpetological Conservation Volume 3, Society for the Study of Amphibians and Reptiles. Salt Lake City, UT.
- 7. Semlitsch, R. D. 2003. Amphibian Conservation. Smithsonian Institution. Washington, D.C.
- 8. Semlitsch, R. D., and J. R. Bodie. 2003. Biological criteria for buffer zones around wetlands and riparian habitats for amphibians and reptiles. Conservation Biology 17:1219-1228.
- 9. Zedler, J., and S. Kercher. 2005. Wetland resources: Status, trends, ecosystem services, and restorability. Annual Review of Environment and Resources 30:39-74.
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