Q: It is well-known that if a bitch urinates on your lawn, you鈥檒l get a brown circle of dead grass, whereas a dog鈥檚 urine does no visible harm. What is the chemical involved and why do only bitches excrete it? Does the same apply to the male and female of other animals (including humans)?
A: When a bitch urinates, she does so striaght onto the ground and empties her bladder in one go. This quantity of urine is enough to discolour the grass.
A male dog, however, only releases small quantities of urine at any one time so that he can spread it out in many different places to mark his territory. He also tends to urinate on vertical surfaces so that some liquid is lost to evaporation and absorption. This means that there will never be as much urine deposited in one spot by a male dog compared with that deposited by a female dog, so the grass remains unharmed.
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It could be argued that one male dog may deposit only a small quantity of urine but that many dogs often urinate on the same spot, so the same discolouring effect should be observed. This is not the case, because the patch of ground has time to recover and disperse the urine deposits before the next visit by a male dog, except in the areas that are most frequently urinated upon, such as busy public parks.