Moving like a buffaloIn a sentence: The North American bison (Bison bison) shapes their habitats through grazing and impact movements (wallowing, herding), resulting in landscape topographic structural changes, vegetation redistribution, and restructuring that impacts other species of vertebrates and invertebrates on the landscape. In an image:  Longer form thoughts: The North American bison is one of the more surprising species on my list of Aquatic Architects. These terrestrial megafauna create open water ponds on the prairie from wallowing behavior. Therefore, they have made it onto my list of animals that engineer or create aquatic structures. However, their behavior, their impacts on the landscape, the effects on other species, and their absolutely fascinating history require, I think, a broader explanation than simply speaking to aquatic architecture. As far as I know, bison don't go about their day considering how and what they will engineer. They engineer just through moving. They have two key behaviors that result in ecosystem engineering: 1) Discriminatory grazing (Towne & Hartnett, 1995; Knapp et al., 1999).and 2) wallowing (McMillan et al., 2000; Truett et al., 2001).. Discriminatory grazing - being a picky eater. Wallowing - bathing in dirt. Bison prefer green grass. As they navigate grasslands, they select the greenest stems, clipping the grass with their teeth. Grasses have different greening times and a tiny window of greening in the Great Plains. In chasing after the green, bison move rather quickly. Not spending too much time in any particular location for grazing, bison move vast distances, minimizing grazing impacts locally. This preference for green and the speed at which they move create a heterogeneous distribution of grasses. Short grass, tall grass, shrubs, and a diversity of species develop a diversity of microhabitats that specialists, such as many grassland bird species, can take advantage of. Many of these birds use bison hair to construct their nests (Coppedge, 2009; Wisentproject Kraansvlak, 2019). The warm, elastic bison fur is probably excellent for eggs for insulation and mechanical protection. I think a fun research study would be to access the thermo-mechanical properties of a bird's nest made out of bison hair to see how that might impact chick survival rates. Where are my ornithologists who took too many physics courses? The increase in small vertebrates also invites small predators - such as foxes and coyotes. Larger predators (grizzly bears, wolves, humans) also move in, attracted by large ungulates (deer, elk, pronghorn antelope, moose) who have benefited from the newly restructured grasslands. As bison move through the landscape, their shaggy coats pick up seeds. This allows them to gather and plant vegetation across the landscape. Many of these natural grasses have deep root systems. These deep root systems act as carbon sinks and stabilize the soil. I'm not a climatologist, but I am aware enough of the conversation surrounding our climate to confidently claim that the restoration of grasslands and reintroducing one of its key engineers could be a practical and critical step in cooling and stabilizing our climate. Our climate catastrophe is a many-pronged problem, and so must our solutions be. Behavioral side note: The biomechanics of how bison eat make them distinct from cattle (Bos taurus) that currently dominate our North American grasslands. Cattle grip and tear up grass root systems, killing the grass. While, as far as I can tell, this is primarily anecdotal, it is a pervasive claim amongst bison managers/ranches, meriting some note and probably more study. Studies on the Eurasian bison (a cousin of the N. American bison) have shown that because of their wide muzzles and muscular tongues, Eurasian bison can clip grasses closer to the ground, preventing disturbance to the root systems. Behaviorally, cattle are less discriminatory (making them easier to raise, but harder on the land) because they graze more uniformly, which decreases biodiversity. Bison also engage in wallowing behavior - particularly males in rut. Bison roll on the ground, bathing themselves in dirt. Through rolling, they often remove all vegetation from that location. These depressions then capture rainwater, fill, and usually become small ponds. These open-water ponds benefit other vertebrates on the landscape, allowing them to drink water. These small ponds (~ 1 m. to 2 m. wide, and ~ 20 cm deep, become microhabitats. These small ponds are home to frogs, snakes, birds, and insects. Because of the higher water content, the vegetation directly around and within the pond differs from the surrounding grassland. These small ponds also support groundwater recharge. While there are practical reasons why bison populations will not fully return to all of their natural ranges in our lifetime, perhaps one way we can compensate for this is by creating buffalo wallows throughout our prairies. Bison biomimicry can extend to more than just excavating ponds in the middle of grasslands; there has also been work done on moving cattle between pastures to mimic the natural movement dynamics of bison to achieve the same heterogeneous grazing patterns bison produce. Not only does the soundscape of a bison-engineered habitat have grassland birds, but it also has the croaks of frogs. Just listen to this video of a Bison wallow. Absolutely lovely. Eat more bison: One of the best ways, I would argue, to promote bison back onto their natural landscapes to engage in the engineering of grasslands and resulting trophic cascades, is to consume more bison. References:
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I've recently become aware of "Hippo Highways". In a sentence: Hippo highways are pathways of cleared vegetation and compacted dirt created by hippos as they move over land from the wetlands they occupy in their search for food, eventually creating a new flow pathway for water, creating new wetlands and changing the vegetation dynamics. In a longer form: The hippopotamus (Hippopotamus amphibius), the very large and dense (they sink) semiaquatic mammal engineers ecosystems just by searching for food. Males are around 3500 lbs to 9000 lbs! The females are a more reasonable 3000lbs. Hippos spend their days in water to avoid the heat of the day. At night, the move onto land and forage for food. And they EAT. But as far as the grazers go they only eat around 1% - 1.5% of their body weight daily. How dainty. If we consider that the average male hippo weighs 5000 lbs and the average female weighs 3000 lbs and live in groups of a 10 - 30 individuals, that would be, on average a thunder of hippopotamus, could be expected to clear around 450 lbs. to 2025 lbs. a night. Which is around 60,750 lbs a month. Start to scale this up to a year or a decade, its easy to imagine how the vegetative and topographic structure of a landscape would have to change and give way. These pathways, repeatedly utilized by other hippopotami (stigmery, anyone?), become cleared of vegetation and depress onto the ground. These trails deepen over time and can become so deep that they fill with water. Once filled, this hippo highways redirect water flow and by extension, redirect nutrients carried within that water. Wetlands are created as water is redirected to new locations while other wetlands dry, leaving behind drained ponds and lakes. This directly impacts other species living within those environments. (Imagine being a fish, relocating to an entirely different pond, navigating through an incised channel). Just by moving on the landscape, hippos create new ecosystems. They drive habitat heterogeneity, spatial and temporal dynamics of the habitats they forage within, and undoubtedly have a tremendous impact for the other aquatic and semiaquatic species that live along side of them. I first looked to Colombia, where hippos are an invasive species, to see if Google Maps could give any insights to the scale of their landscape engineering... but the resolution and frequency of scans wasn't clear to me. Fun fact: Pablo Escobar illegally imported many species to his private ranch/zoo In Colombia, including hippos, making them the largest invasive species on the planet. So I looked to Google Earth Imagery of the Okavango Delta. The scale of the landscapes hippos engineer breaks my mind a bit. Look at these things. Massive. (The width of these images is about a 1 km wide) Stunning how dynamic these foraging pathways are. I imagine that these pathways also make the hippos more resistant to drought conditions, localizing water in low point and help them navigate water when the water is high, allowing them to move along already established pathways.  I'm devastated that something friend-shaped has zero tolerance for human friendship. Citing my sources:
McCARTHY, T. S., ELLERY, W. N., & BLOEM, A. (1998). Some observations on the geomorphological impact of hippopotamus (Hippopotamus amphibius L.) in the Okavango Delta, Botswana. African Journal of Ecology, 36(1), 44–56. doi:10.1046/j.1365-2028.1998.89-89089.x Castelblanco-Martínez, Delma Nataly, et al. "A hippo in the room: Predicting the persistence and dispersion of an invasive mega-vertebrate in Colombia, South America." Biological Conservation 253 (2021): 108923. Google Earth Pro. (2004, 2011, 2013, 2016, 2018, 2020, 2023). Location: -19.65206112, 22.92836752. Available through: Google Earth. Accessed September 18, 2024. [https://earth.google.com/web/@-19.65206112,22.92836752,-49553.62807974a,51303.82162909d,35y,0.0002h,0t,0r/data=CgRCAggBSg0I____________ARAA] |
AuthorJordan is a technologist, an Indigenous futurist, a beaver futurist, an animal enthusiast, a curious scientist, a compulsive engineer, and science storyteller. 
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