Hippo Highways

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]