My cat used to drink from the garden pond and never seemed to suffer any ill effects, and you often see dogs drinking from muddy puddles. So why do humans have to be so careful and only drink clean water? (Continued)
• Dogs prefer puddles because tap water smells of chemicals. To get an idea of this, fill a 2-litre bottle with tap water and leave it for a few days. Then shake the bottle so bubbles on the inside rise to the top. Unscrew the lid while your nose is very close to the neck of the bottle and you will get a hint of odours that dogs dislike.
As far as water cleanliness goes, humans have a longer intestine than dogs, so any pathogens will have more time to multiply in our gut and cause illness.
Advertisement
Don Trower
Braintree, Essex, UK
We pay £25 for every answer published in ¿ìè¶ÌÊÓƵ. To answer this question – or ask a new one – email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
¿ìè¶ÌÊÓƵ retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.
You can also submit answers by post to: The Last Word, ¿ìè¶ÌÊÓƵ, 25 Bedford Street, London WC2E 9ES.