A blue whale's song can travel 1,600 kilometres through the ocean. A lion's roar carries 8 kilometres across the savannah. A tiny river otter's call barely reaches one kilometre. Why do some animals communicate across vast distances while others are confined to metres? A landmark study published today in the *Journal of Mammalian Evolution* has found the answer — and it's elegantly simple.
Researchers at UNSW Sydney, led by Dr. Ben Walker, an evolutionary ecologist, analysed data from 81 scientific papers covering 103 mammal species across the globe. Their goal: to understand what drives the evolution of long-distance communication. The results reveal two distinct rules — one for land, one for water — that together explain the extraordinary range of mammalian calls.
**The Land Rule: It's About Your Environment**
For land mammals, the biggest evolutionary driver of how far a call travels isn't the animal's size. It's the environment it lives in. And the pattern is surprising.
You might expect open environments — savannahs, grasslands, tundra — to favour long-distance calls. After all, there's nothing in the way. But the study found the opposite: mammals living in closed environments like rainforests evolved further-reaching calls than those living in open ones.
The reason appears to lie in the acoustic properties of dense vegetation. Rainforests absorb and scatter sound — which means only the most powerful, well-structured calls can travel far. Over evolutionary time, this creates strong selection pressure for animals that can punch through the noise. Open environments allow even modest calls to travel reasonably well, so the evolutionary pressure is lower.
The second key factor for land mammals is home range size. Animals with larger territories evolved calls that travel further. A roaring lion isn't just communicating with its pride; it's broadcasting its territorial claim to rivals kilometres away.
**The Ocean Rule: It's About Your Body**
For aquatic mammals, the pattern is different and remarkably simple. Body size is the dominant factor: the larger the animal, the further its calls can travel.
Blue whales — the largest animals ever to have existed on Earth, weighing around 150 tonnes — produce calls that travel up to 1,600 kilometres. Dolphins, perhaps 150 kg, communicate over hundreds of metres. River otters, at around 28 kg, reach about a kilometre.
The ocean is a uniquely efficient medium for sound — it travels five times faster in water than air and loses energy far more slowly over distance. In this environment, physical size translates almost directly into acoustic power.
**A Conservation Warning Hidden in the Data**
The research carries an important implication for whale conservation. Human activities that stunt the growth of whales — historical commercial whaling, vessel strikes, marine pollution — don't just reduce population numbers. They may also reduce the ability of whale populations to communicate.
If a whale grows smaller than it would naturally, the study's findings suggest its calls will be shorter in range. In a species that relies on long-distance song to find mates across ocean basins, that's a serious reproductive threat. Dr. Walker's team noted this explicitly — adding a new dimension to why protecting large marine mammals from anthropogenic harm matters.
**Why This Changes How We Think About Animal Communication**
This study is unusual in its scale: 103 species, 81 papers, analysed together to find universal evolutionary patterns. The finding that different rules govern land and aquatic mammals suggests that the evolution of communication depends fundamentally on the medium through which sound travels.
Land and water have driven mammalian communication down two distinct evolutionary paths over millions of years. For land mammals, the environment shapes the call. For sea mammals, the body shapes the call. Together, these rules explain the full spectrum — from a mouse's ultrasonic squeak to the planet-spanning song of the blue whale.
As climate change alters habitats and acidifies oceans, monitoring how species' evolved call strategies adapt — and protecting the conditions in which they evolved — becomes meaningful conservation work.
The study was published in the *Journal of Mammalian Evolution* on March 10, 2026, by Dr. Ben Walker and colleagues at UNSW Sydney. 🐋
*Sources: UNSW Sydney News (March 11, 2026) · Journal of Mammalian Evolution · newscop.com.au*
