New research by evolutionary biologist Kathryn Lord at the University of Massachusetts Amherst suggests the different behaviours are related to the animals' earliest sensory experiences and the critical period of socialisation.
Until now, little was known about sensory development in wolf pups, and assumptions were usually extrapolated from what is known for dogs, Lord explained.
This would be reasonable, except scientists already know there are significant differences in early development between wolf and dog pups, chief among them timing of the ability to walk, she added.
To address this knowledge gap, she studied responses of seven wolf pups and 43 dogs to both familiar and new smells, sounds and visual stimuli, tested them weekly, and found they did develop their senses at the same time.
Her study also revealed new information about how the two subspecies of Canis lupus experience their environment during a four-week developmental window called the critical period of socialisation, and the new facts may significantly change understanding of wolf and dog development.
When the socialisation window is open, wolf and dog pups begin walking and exploring without fear and will retain familiarity throughout their lives with those things they contact.
Through observations, Lord confirmed that both wolf pups and dogs develop the sense of smell at age two weeks, hearing at four weeks and vision by age six weeks on average.
However, these two subspecies enter the critical period of socialisation at different ages. Dogs begin the period at four weeks, while wolves begin at two weeks.
Lord reports for the first time that wolf pups are still blind and deaf when they begin to walk and explore their environment at age two weeks.
She said, "when wolf pups first start to hear, they are frightened of the new sounds initially, and when they first start to see they are also initially afraid of new visual stimuli. As each sense engages, wolf pups experience a new round of sensory shocks that dog puppies do not".
Meanwhile, dog pups only begin to explore and walk after all three senses, smell, hearing and sight, are functioning.
"It's quite startling how different dogs and wolves are from each other at that early age, given how close they are genetically," she said.
