Ants: A Closer Look
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Why ants?
Ants, which we so often think of as pests, are actually very important ecosystem engineers.
However, ants in fact provide a variety of ecosystem services and the many ant species found at Prairie Creek represent a vital aspect of the ecosystem.
Ecosystem Services
Ant species diversity helps foster and improve various ecosytem services services including: filtering water, improving soil health, improving biodiversity, cycling energy through ecosystems and directly benefitting human wellbeing.
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Sources: Kittelson et al., Sanford et. al.
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Filter Water
The tunneling and activity of ants improves the filtering quality of the soil.
Improve Biodiversity
Ant species richness helps increase plant species diversity because ants pollinate and disperse plant seeds.
Improve Soil Health
Ants improve the soil health by bioturbation - meaning when they return organic matter to soil. Additionally, thatched ant mounds increase soil nutrient availability by improving mineralization rates of nitrogen and organic matter in the soil.
An example of a thatched ant mound
found at Prairie Creek, Spring 2016
Cycle Energy Through Ecosystems
Ants are prey to many species in addition to being omnivores and decomposers. In addition, ant tunneling redistributes energy in the ecosystem
Directly Benefit Human Wellbeing
Ants provide a significant source of protein in some parts of the world.
Biomedical Services: ant venom is used in biotechnological and pharmaceutical developments.
Survey of Ants at Prairie Creek
Findings
The Carleton College students studying the ants at Prairie Creek found that an abundance of large red and black ants live near the limestone quarry.
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These ants are thatching ants (Formica obscuripes), which among other things, are known to prey on arthropods, eat honeydew, and build thatched mounds.
Baits
To attract and survey ants, students used various baits and counted ants in ten-minute intervals over an hour.
Peanut butter (with some traces of jelly) only ever attracted about 10-15 ants to the bait.
Jelly was unsuccessful at attracting ants.
Honey was highly successful at attracting ants in the small quarry on top of a hill in the prairie. The honey attracted between 50-100 ants to the baits set up.
Ants attracted to the bait near the quarry appeared to be the same kind of ant: large with a reddish head and a black body.
Honey attracted between 50-100 ants to the baits.
Peanut butter (with some traces of jelly) only ever attracted about 10-15 ants to the bait.
Jelly was unsuccessful at attracting ants.
Honey attracted between 50-100 ants to the baits.
Ant Location
Ants are abundant at the top of the hill in the prairie around this small limestone quarry.
Ants are abundant at the top of the hill in the prairie around this small limestone quarry.
Two students at the cultivated field that did not attract any ants.
Ants are abundant at the top of the hill in the prairie around this small limestone quarry.
Prey
Students filmed ants preying on larva and grasshopper, concluding that these ants are omnivores (and bite humans).
Larva
When ants prey on the larva, groups of them drag their prey to underground tunnels.
Grasshoppers
Ants prey on still-alive creatures.
Ants are abundant at the top of the hill in Prairie Creek around the small limestone quarry.
Ant Identification Process
With the advice of Carleton's entomologist David Hougen-Eitzman, students collected a sample of ants, stored the ants in ethyl alcohol and brought them back to the biology lab to observe under a microscope.
Using an ant key created by Carleton students who studied and identified different types of ants in the Arboretum and McKnight Prairie, these ants were identified to be thatching ants, or Formica obscuripes (obscuripes mean dark or blackish legs).
Students collect a sample of ants using an aspirator to suck up ants into a container to be brought back to the biology lab.
Students collect a sample of ants using an aspirator to suck up ants into a container to be brought back to the biology lab.
After storing ants in ethyl alcohol, students bring them back to the biology lab to observe under a microscope.
Students collect a sample of ants using an aspirator to suck up ants into a container to be brought back to the biology lab.
Thatched Mounds vs. Limestone
Further question: Why were there no obvious thatched mounds around the limestone quarry where there was an abundance of ants?
Ants rely on their environment to regulate their body temperature, which is why one can find many ants under rocks (they use them as solar collectors). This perhaps explains why ants were found under the limestone in the quarry.
An excellent task for future research would be to look for thatched mounds around Prairie Creek built by Formica obscuripes.
Other Facts About Ants
Measure Success of Prairie Restoration
The Kittelson, Priebe and Graeve study from Gustavus Adolphus College focused on ants in prairies in southern Minnesota. Their study sites included a prairie that had been previously reconstructed from an agricultural field and a prairie remnant that had never been plowed, but was undergoing rehabilitation.
Compared to the prairie undergoing rehabilitation, the reconstructed prairie had the following features:
- Higher ant species diversity
- Higher plant species richness and diversity
- Lower disturbance at borders
- More frequent ant encounters
- Less dense and more organic rich soil
Though other factors cannot be ruled out, many of these qualities can likely be attributed to the presence of ants. Their presence is correlated with a lack of disturbance. It is unclear whether the rich ant population is also due to the diversity of plants or the other way around, but they certainly go together.
Understand Sensitivity to Human Contact
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Prairie Creek WMA is intended to welcome visitors, researchers and recreation. If ant populations are meant to be protected, their sensitivity to human contact must be considered.
- Ant species richness was attributed partially to the lack of human disturbance. (Kittelson et al.)
- Significantly fewer ants are found in fragmented habitats with many edges. (Sanford et. al.)
- Ants are vulnerable to nearby urbanization. They are affected by environmental alterations in surrounding landscapes. (Sanford et. al.)
References:
[1] Del Toro, Isreal, Relena Ribbons, and Shannon Pelini. "The Little Things That Run the World Revisited: a Review of Ant-mediated Ecosystem Services and Disservices (Hymenoptera: Formicedae)." Myrmecological News 17 (2012): 133-146.
[2] Kittelson, Pamela, Monica Priebe, and Phillip Graeve. "Ant Diversity in Two Southern Minnesota Tallgrass Prairie Restoration Sites." Journal of the Iowa Academy of Science 115 (2008): 28-32.
[3] Sanford, Monte, Patricia Manley, and Dennis Murphey. "Effects of Urban Development on Ant Communities: Implications for Ecosystem Services and Management." Conservation Biology 23.1 (2009): 131-141.