If the offspring is a female, it means she got an X chromosome from her mom, and an X chromosome from her father.
To me, this sounds like the Garter Snake is becoming more immune to this toxic chemical.
C. Genetic variation
Bacteria are very numerous, and random mutation of bacterial DNA generates a wide variety of change, including resistance. It happens through mutation and selection. Not only are they capable of sharing genetic bits of DNA to related and unrealted species they can develop ways to remove the antibiotic before it reaches its intended area via biochemical pumps or enzymes to inactiavte the antibiotic.
