What Animals Reshape Earth's Waterways?

Eco engineers are animals that vastly change the ecosystems they live in when they create their preferred habitats. Learn about a few, from hippos to tiny crabs, in this episode of BrainStuff, based on this article: https://animals.howstuffworks.com/animal-facts/5-animals-that-can-reshape-waterways.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff Laurin
Vogel bomb here. Nutrients, water, and living space are some
of life's basic needs, so anything that alters their distribution
is going to be a key factor in our struggle
for survival. A change the waterways, the landscape, or the

(00:24):
availability of food, and an entire ecosystem can be reshaped.
Certain species wield that power to great effect. One of
the most fascinating topics in biology is the role of
ecosystem engineers. These are organisms that either directly or indirectly
alter their physical surroundings in ways that have major impacts

(00:46):
on the livelihood of other organisms. Take, for example, the
American alligator. Out in the wild, these big reptiles like
to make their own swimming pools. Using their snouts and claws,
they create massive trend known as gator holes in the
limestone around Florida's Everglades. In short order, they flood with water.

(01:07):
They also tend to remain full of water even well
into the dry season, a time when standing water can
be scarce for other life forms. A gator hole can
provide a badly needed oasis of frogs and turtles move
into these convenient little ponds while plants around their rims,
attracting all kinds of insects. So, as unlikely as it

(01:27):
may sound, Florida alligators are environmental stewards. They create brand
new homes for their neighbors and in the process, strengthen
the biodiversity of the everglades. Other ecosystem engineers leave different marks. Today,
we're looking at a few that reshape rivers, link ponds together,
and transform mangrove creeks. Map makers of the world. You'll

(01:50):
want to keep your erasers handy when these beasties come to town.
First up beavers. The term busy as a beaver really
should be considered high. Beavers are hard working rodents. A
lone one can cut down up to two hundred trees
in a single year. Famously, they build sturdy homes or
lodges for themselves out of branches, mud, and other materials.

(02:13):
They can also make their own large scale ponds by
damming streams, and this works by creating a backlog of
water upstream of the dam. The resulting pond not only
gives beavers a place to build their lodge, it also
affords easy access to surrounding trees. Often around a foot
or a third of a meter, of water covers the
bases of nearby pines and hardwoods that once stood on

(02:36):
dry ground. As a result, beavers can swim right up
to these trees. They also like to dig canals that
branch out of the new ponds, penetrating deep into the
local forest. These new wetlands provide homes for smaller animals
like amphibians. Plus, the dams make great natural filters, a
blocking excess nitrogen from our creeks and streams. However, all

(03:00):
of the side effects are positive. When a beaver dam fails,
it's liable to flood towns or farms. The aftermath can
be expensive. In the southeastern US alone, these floods are
responsible for an estimated twenty two million dollars a year
in damages to the timber industry. It's not surprising, then,
that many people view beavers as pests. If you have

(03:21):
a beaver problem, do know that humane solutions are out there.
Next up the adorable yet terrifying hippopotamus. Put a group
of hippos and a floodplain with lots of nice, soft soil,
and they'll start reconfiguring the turf. That's because hippos have
unique skin that needs to be kept wet for most

(03:41):
of the day or they'll become dehydrated, so they plow
through the reed beds that ring rivers and lakes, creating
deep wallows of water and mud that keep them cool
during hot days. They're too heavy to float or swim,
so they reshape the soil bed beneath the water to
walk along it, the tops of their heads poking out. However,

(04:04):
these wallows don't offer much in the way of food,
so at night hippos leave their comfy wallows to go
grazing on dry land, returning before the sun. That daily
coming and going creates deep depressions in the soil near
bodies of water, which in turn become channels worn down
over time. These footpaths can be as much as sixteen

(04:26):
feet that's five meters wide, and just like gator holes,
they're quick to fill up with water. Oh what's more,
hippo highways linking ponds and streams to big rivers can
also be established. If the area should flood, these connection
points may become an outlet for surging water. They also
enable swamplands to expand and under the right circumstances, The

(04:48):
trench like trails can divert a great deal of sediment
from rivers into ponds. And that's not all that hippos
are doing as they go about their business. Pun intended
fifteen analysis determined that hippo dung is an important source
of nutrition for at least some of the fish and
insects that share the animal's native range. Never underestimate the

(05:09):
power of poop. However, for their size, hippos don't actually
eat a lot, only about one to one and a
half percent of their body weight every day. Large cattle
eat more like two and a half percent, and African
elephants can eat over four percent, which is no joke
when you weigh some seven tons. On a typical day,
an adult elephant will spend twelve to eighteen hours eating,

(05:31):
which is vital to the ecosystem. Elephant dung is a
nutritious fertilizer for the soils of Africa. It's also a
vehicle by which many seeds are dispersed. Furthermore, by knocking
down trees and eating shrubs, these colossal animals convert forests
into grasslands, and a two thousand and nine study published

(05:53):
in the journal Bioscience revealed even more about the transformative
powers that African elephants have over their habitats. Sort of
similar to hippos, Elephants are great at building water channels.
The test herbivores cover the same land routes over and
over again as they go about finding food and water,
making trails in the process. Sometimes multiple generations of elephants

(06:15):
will reuse the exact same footpaths. As time goes by,
the animals compress the soil, turning their walkways into trenches,
and when elephants move back and forth between bodies of water,
their sunken trails become nice conduits. Thus, rivers or ponds
that were once isolated can be merged via elephant made canals,

(06:37):
providing inroads for other wildlife to travel. And another study
of Asian elephant trails in Thailand found that these paths
can divert monsoon run off into local streams, preventing flooding.
But enough of mammals and reptiles. A number of crustaceans
are great diggers, including fiddler crabs, which shelter in tunnels

(06:58):
measuring up to three feet or more in that's about
a meter. The holes are quite a construction project. Given
the fact that most fiddler species are less than two
inches or five centimeters wide, then there are the various
species of burrowing crabs of the mangrove swamps and salt
marshes of the world. The tunnels that these small crabs

(07:18):
build are liable to weaken the surrounding turf. On mangrove
swamp shorelines, this has the effect of widening tidal creeks,
whose mud and clay based banks are rendered more vulnerable
to erosion by the digging invertebrates. They may also play
a key role in aerating the marshy soil and kicking
up nutrients from the beds, and that's just part of

(07:40):
the story. Because burrowing crabs have such a profound effect
on sediment composition, their tunnels can also cause completely new
creeks to form within these mangrove systems, and all of
this further impacts the plants and other animals that live
around those environments. Those tiny crabs change how microorganisms in
places can grow, which changes what foragers and predators come

(08:03):
to the area. Just another example of how small actions
can add up to huge effects. Today's episode is based
on the article Eco engineers five animals that can reshape
Earth's waterways on how stuffworks dot Com. Written by Mark Vancini.
Brain Stuff is production by Heart Radio in partnership with

(08:24):
how stuffworks dot Com and is produced by Tyler Klang.
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