Good evening and thank you for reaching out. Our sincere apologies for the delay in responding. Our experts are quite busy out in the field at the moment, but we do typically respond sooner. Our apologies as I said. In the meantime, I’m going to provide you with several links to some information about snakes  That you may find helpful and useful. :

https://search.msu.edu/index.php?q=Garter+snakes#gsc.tab=0&gsc.q=Garter%20snakes&gsc.page=1   
best,

Hi, 

Apologies for the delay in responding. Garter snakes and other snakes tend to occur in an area for three reasons - the area provides food, water, or shelter of some sort. If an area does not provide any of these three things, garter snakes will likely not occur or spend very much time in such an area. 

In terms of food, garter snakes eat a variety of prey items - for example, earthworms, amphibians (frogs and salamanders), leeches, slugs, snails, insects, crayfish, small fish, and other snakes. Garter snakes help control populations of these species. 

Suitable shelter for garter snakes would be any kind of natural vegetation (tall grass, shrubs), dead vegetation, woody debris (logs, brush piles, wood piles, rock piles, etc.), basically anything that can provide natural (or artificial) cover for the snakes. 

Hope this information helps. Please let me know if you have any additional questions or would like any additional information.

Best,

Yu Man