The plural of deer is deer.
A hooved, grass-eating mammal of the Cervidae family. Most male deer have antlers.
The word "deer" can be used as both a singular and a plural noun in English. When "deer" is used to refer to a single animal, it is a singular noun, and when it is used to refer to multiple animals, it is a plural noun.
In general, the word "deer" is used as the plural form of the word when it is referring to a group of deer that are all of the same species. This is the most common way to use the word "deer" as a plural noun.
Despite Merriam Webster online dictionary listing deers as an acceptable plural form of deer, as you can see from the graph, the word has rarely, if ever, been used in written English since 1900.
None of the other major dictionaries list deers as an accepted form.
It's safe to say that you should use the word deer and not deers.
The word "deers" is not a commonly used plural form of "deer." While "deers" is sometimes used as a variant of "deer," it is generally considered to be incorrect or archaic.
Here are some examples to illustrate the difference between the singular and plural forms of "deer":
"I saw several deer in the forest this morning." (This sentence is talking about more than one deer.)
"The deer are known for their graceful movements." (This sentence is talking about the characteristics of a group of deer.)
The graph shows the occurances of the plural of deer in written English since 1800 using Google's Ngram Viewer.
The only animals in the world to grow antlers are deer. Of all species of deer, only in Reindeer do the females also have antlers.