The amount of toxin needed to poison an animal is often dependent on which of the following factors?

Focus on body mass: Body mass is a critical factor because it determines the volume of distribution for the toxin within the animal's body. Larger animals have more tissue and fluid to dilute the toxin, requiring a higher dose to achieve the same effect.

Consider the principle of dose per unit mass: Toxicologists often calculate the effective dose of a toxin using the formula: $D=d\times m$, where $D$ is the total dose, $d$ is the dose per unit mass, and $m$ is the animal's body mass.