The Inner Life of Animals

Peter Wohlleben, a German forester who manages woodland near the village of Hümmel in the Eifel mountains, draws on decades of professional experience and personal animal husbandry to argue that animals possess rich emotional lives comparable to those of humans. Because evolution builds on existing genetic programming rather than inventing new biology for each species, Wohlleben contends, the emotional hardware found in humans also exists in other animals. He acknowledges that science cannot definitively prove animals feel the same way people do, but counters that science cannot prove any two humans share identical feelings either. He aims to translate academic research into accessible language, combine it with his own observations, and show that animals are complex beings capable of love, grief, and joy.

Wohlleben opens with maternal love, recounting how a squirrel mother near his forest lodge in 1996 struggled across a sunlit lawn with a baby clasped around her neck, collapsing repeatedly from exhaustion. He explains that the same hormones driving human maternal bonding, particularly oxytocin and endorphins, operate in goats and other mammals. A personal anecdote illustrates the fragility of this bond: When one of his newborn goat kids slipped under a stall door and its birth mucus dried before the mother could lick it clean, the mother refused to accept the baby.

From maternal love, Wohlleben turns to instinct, challenging the assumption that instinct-driven feelings are inferior to conscious ones. He cites a 2008 Max Planck Institute study using MRI scans, which revealed that test subjects' brain activity indicated their decisions up to seven seconds before they became consciously aware of making them. Because emotions are fundamentally the language of the unconscious, Wohlleben argues, their instinctive origin does not diminish their intensity. He bolsters this point with cross-species adoption cases: a crow in Massachusetts that fed an orphaned kitten for five years, and a French bulldog in Germany that adopted six wild boar piglets.

Wohlleben surveys the neurological basis for animal emotions, identifying the limbic system, an evolutionarily ancient brain region shared by many mammals, as the seat of emotional processing. Researchers have found over 20 pain receptors around fishes' mouths and fear-processing structures in goldfish brains comparable to the amygdala, the brain structure responsible for processing fear in humans. Birds lack the neocortex, the outer brain layer associated with conscious thought in humans, yet achieve high-order cognition through a different structure called the dorsal ventricular ridge; ravens can match or exceed the mental abilities of primates.

A chapter on pigs and wild boar connects intelligence to ethics. Wohlleben cites GPS-tracking research showing that wild boar recognize family members and allow territorial overlap with relatives while excluding strangers. He describes a sow at the University of Veterinary Medicine in Vienna who gave birth to 160 piglets, taught them all to build straw nests, and later served as a midwife for her daughters. Wohlleben suggests that public awareness of pig intelligence would make many people lose their appetite for pork.

The book surveys a wide range of emotions and cognitive abilities. On gratitude, Wohlleben tells the story of adopting Barry, a nine-year-old cocker spaniel passed through multiple owners, whose lasting happiness in his final home seemed inseparable from appreciation. He also describes crows in Seattle that brought a young girl reciprocal gifts after years of being fed. On deception, he recounts his rooster Fridolin's habit of faking food-discovery calls to lure hens close enough for surprise mating, and research showing that male swallows issue false alarm calls to prevent their mates from straying. On thievery, he describes Eurasian jays choosing quieter sand over noisy gravel to bury food caches when rival birds are within earshot.

Wohlleben argues that animals display distinct personalities, contrasting his fearful cocker spaniel Barry with a fawn that charged his normally courageous dog Maxi, forcing her to flee. Research on great tits confirms that both bold and shy temperaments confer survival advantages, with shy birds noticing food sources that bolder birds overlook. Further evidence of individuality emerges through naming: Experiments at the Friedrich-Loeffler-Institut showed that pigs trained to respond to individual three-syllable names achieved a 90 percent success rate, with only the named pig reacting while others remained calm.

The book's middle chapters address empathy, fairness, and grief. McGill University researchers found that mice who had observed other mice in pain experienced significantly more pain themselves, an effect that depended on familiarity and was transmitted through sight. Pigs conditioned to associate music with rewards transmitted their emotional states to newcomer pigs who had never heard the music. At the Budapest Zoo, a brown bear pulled a drowning crow from its moat, then returned to its vegetables, ignoring the bird as food. On fairness, dogs in a Vienna experiment refused to cooperate when they saw a companion rewarded for the same task they performed without reward. Ravens refused to work again with partners who had stolen both pieces of cheese in a cooperation task. Wohlleben also describes grief in red deer: When an alpha doe, the herd's experienced lead female, loses her fawn, she returns repeatedly to the site of death, calling for her young, in a process that parallels human mourning. Her grief endangers the herd by keeping it near the site of danger, prompting a seamless transfer of leadership to another experienced doe.

Wohlleben extends his inquiry to fear, describing wild boar in the Swiss canton of Geneva that swim across the Rhône River to escape French hunters each fall. This tradition has persisted across generations since Geneva banned hunting by referendum in 1974. Hunted animals in Central Europe have become almost exclusively nocturnal not by nature but by adaptation, and research suggests that traumatic experiences attach chemical markers to genes, potentially transmitting fear-based behaviors to offspring. On altruism, Wohlleben presents research showing that vampire bats regurgitate blood meals not only for close relatives but for unrelated cave mates, preferentially helping those who have helped them in the past, evidence that sharing involves genuine choice rather than genetic programming.

Later chapters examine how animals perceive the world in radically different ways. Moths use furry coats to scatter bat sonar, pigeons see polarized light that functions as an ever-present compass, and dogs may compensate for relatively poor visual acuity with hearing 15 times more sensitive than humans'. Wohlleben also addresses artificial environments, explaining how artificial light traps moths in fatal spirals and roads kill approximately 250,000 wild animals annually in Germany. Cities, meanwhile, are becoming ecological refugia, places where species persist and rebound despite surrounding development. Berlin hosts one of the world's highest populations of goshawks, and scientists estimate that about 50 percent of native plant species in the Northern Hemisphere now grow in urban areas.

On communication, Wohlleben cites research showing horse whinnies contain two basic frequencies: one indicating whether an emotion is positive or negative and another conveying its intensity. He discusses Koko, a female gorilla trained in sign language by Penny Patterson at Stanford University, who learned over 1,000 signs, but argues that the larger scientific failure is neglecting to learn animal languages rather than teaching animals human ones.

The book's final chapter asks whether animals have souls. Wohlleben adopts a secular definition of soul as the principle of life, feeling, thought, and action, and argues that animals clearly qualify. He offers a philosophical argument as well: Because evolution produced humans through gradual change rather than an abrupt break, there is no point in the lineage from bacteria to humans at which a soul could have first appeared. If humans have souls, so must other creatures.

In the epilogue, Wohlleben acknowledges the ethical dilemma that recognizing emotions in animals complicates all food choices. He identifies resistance from scientists defending established positions and politicians protecting factory farming and hunting practices, and rejects the charge of anthropomorphism by noting that humans are biologically animals. He closes by urging readers to treat animals with greater respect, suggesting that the resulting happiness in the animals around us will trigger a corresponding happiness in ourselves.