Why you shouldn’t let your pet lick your face!

Upper Elementary Science Fair Project -bacteria growing

Do you LOVE when your pet licks your face OR does it gross you out?? Which pet has the most bacteria in it’s mouth?

Choosing project

Sometimes it can be quite a challenge to come up with a subject for the school science fair. When it was time for my oldest daughter, who is in fifth grade at the moment, to think of a project for the upcoming science fair at, we started looking at Pinterest (my absolute favorite search engine). There are tons of really cool experiments to find online, but the problem is: you want to stand out and do something a little bit different than everyone else. Right?

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Then I stumbled upon this blog post by “No time for flash cards”. They performed a different kind of experiment, but this project was the starting point for us. We saw lots of different bacteria growing experiments, but not the exact one we performed (even though it has probably been done many times before).

My oldest is an absolute pet lover! She adores all animals! She decided she would like to find out what pet carries the most bacteria in it’s mouth. That became her question.

Which animal carries around the most bacteria in its mouth?

I quickly ordered pre-filled agar plates from Evviva Science on Amazon. According reviews this specific kit was supposed to be the best. I agree and I would definitely buy again. Click here if you would like to check them out.

My daughter’s hypothesis was:

I think the cat has the most bacteria in its mouth, because it eats rodents and birds. Rodents and birds carry LOTS of bacteria.

Needed for bacteria growing science fair project:

• dog
• cat
• horse
• goat
• pre-filled agar plates
• sterilized cotton swabs
• lamp to keep bacteria warm

Steps

Then she carefully rolled the cotton swab on a pre-filled agar plate to get all the potential bacteria to stick.

Finally she put the samples under a warm lamp for 5 days. She recorded and took pictures every day to see how much the bacteria grew. Ideally the temperature is to be kept between 84 and 100 degrees Fahrenheit. If it’s colder it will just take longer to grow. If the temperature exceeds 100 degrees, it might kill the bacteria.

Findings

Below are the pictures she took during the process. It is kind of gross, but not as bad as I would have thought! Before going any further I would like to state that we aren’t real scientists and therefore we can’t explain exactly what kind of bacteria this is. We don’t claim this to be 100% correct. These are just our observations and thoughts.

Dog

day 1

day 3

day 5

Horse

day 1

day 3

day 5

Goat

day 1

day 3

day 5

Cat

day 1

day 3

day 5

Conclusion

My daughter’s hypothesis was proven wrong. To our surprise the results of our bacteria growing showed the cat to have THE LEAST bacteria in it’s mouth. The dog had the MOST bacteria, the horse came in second place and the goat in a close third place.

My daughter’s conclusions were:

“The dog probably had the most bacteria in its mouth, because dogs do lick themselves everywhere and the specific dog I took a sample from eats rodents from time to time. Both of those contain much bacteria. I think the horse came in second place because some horses actually do eat their own excrement sometimes. I really don’t know why the goat came in third place, but my guess is that goats always try to eat everything. They are also kept outside and probably get some dirt in their mouths. The cat I used for my experiment is an outdoor cat that sometimes eats rodents and birds. However, when I took the sample I don’t think she had caught anything that same day. She might only have eaten a little regular cat food or nothing at all.”

Now she only had to write everything on her board, including putting up all the pictures!

My daughter’s presentation at the science fair

Things we would do differently

We took bacteria samples several times. When it came to the samples she was actually supposed to bring to the presentation, we ran out. I was going to order more, but to our surprise Evviva Sciences were out of them too! I had to order from somewhere else (Thank you Amazon Prime!). These other agar plates looked exactly the same, but the bacteria seemed to grow slower. I put the lamp closer to the bacteria to make them grow faster and as a result I might have killed a couple of them… We quickly made new ones, but they were only on the first day at the time of the presentation.

All in all both me and my daughter were very satisfied with the results. She got good grades on the project AND -most importantly- she had a lot of fun with it!

My tip to you is to pick a subject your child REALLY finds interesting! The fact that my daughter loves animals added another layer to this project.

So, after seeing this: WOULD YOU STILL LET YOUR PET LICK YOUR FACE??

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