Most female animals will fight against all odd's to protect the babies in their homes, even of a different species. Tara must have had a strong maternal bond for the boy..
I experienced this first hand when my dog Velvet used to protect our kittens from anything she thought would harm them, and would curl up with them as they slept. Momma kitty had passed during delivery and Velvet immediately took over the maternal role and raised them as kitty pups.. was Quite a sight watching 5 kittens following a big blue hair chow around like a line of ducks across our property.