The chance for eggs to drop off guardians I have found is 20%.

I like to have a number when searching for rare items so I found it.

There is a 20% on a single monster for an egg to drop. About every two of ten monsters will have an egg, twenty of one-hundred will give eggs, and so on.

 This is how I came to that number...

Below are the sets of monsters I killed and the number of eggs I got from each set.  Each set is ten monsters, below is the number of eggs I got from them. Each set has been collected only with a level 50 pet on grasslands.

Set one    Set Two   Set Three  Set Four  Set Five 

3                 3                2                  2               0            

Set Six   Set Seven   Set Eight   Set Nine  Set Ten

4               1                   1                  2              1

I now added 0 behind each number as eggs as it is no longer out of ten but out of one-hundred. I did not add the zero, because if it was zero percent then no one would be getting eggs. I then went and found the mean and median of all the eggs, which was 21.1, median is 20. So I can assume the average percect for eggs is 20%. Correct me if I am wrong here.

Other egg info others and I have found...

It does not matter if you kill, keep alive, or see hoppers. Eggs will still drop/not drop regardless.

To have your eggs count you must purchase items with them at Warlock Exhange Station. Make sure to turn in your eggs before the event ends.

All biome guardian's will drop eggs. Temple guardians do not count.

The salamanders will drop eggs even if they are not guardin a chest.

Multiple eggs can be found on a single island.

I have found 0-7 guardians can be on one island.

What are the salamanders?

Also, the islands didn't have the black covering it earlyer. Now they do!! I hate it!! I thought that Beastkeeper gave us an update....

Whats a level fifty island? Monues, how did you get 38 eggs?!?!? I only got 9.

Salamanders are these guys:

I think I answered yours or someone else question about that being a random chance of a travelling magician staying at your inn. They remove the black fog.

Level 50 island is an island with a level 50 pet, the largest sized island.

I have been bringing my exploration group to the island as often as they have the energy. I am stocking up on the fish eggs and some other nifty things.

@Monues

Lol, Looking at that I must be really unlucky. I've sometimes gone through over 20+ guardians and only gotten a single egg or two.

So, what pets are people exploring with?

I'm doing my watch flock once each day and my lvl50 GP3s and lvl40+ GPs whenever they have enough energy.

I've found way more eggs (even 2-3 in the same island) with my lvl 50 pets. My global result with 12 under lvl 40 pets was of only two eggs.

I found 3 eggs for the first 20 islands I searched. The pets I used ranged from level 50 to level 10. 

Is that a good ratio or not you think?

Really depends on luck how islands are generated. But in average it looks like 5-6 eggs per 20 islands for me (level 30-50 pets, should be a bit more if it's only 50's). It may be 10 islands in a row with no luck and then 2 eggs on the same island. I need to start logging the defetaed guards and their number per island like Monues did (great idea btw!). I also need to restock my Rainbow Jars after the exhibition (used them all, lol), so explore event is quite in time for me.

Ok cool that makes sense. Most of my eggs have been given by the Cygnon Guardians, so I am pretty sure most of mine will come from them.

I was mostly using the grasslands for the first part of the event, like many of you. But, I got like, 30 islands in a row with really good pets and no eggs. I just started randomely using biotypes and discovered that you should use the jungle. It's really worth it- I got 3 eggs per island on average for a while and then went down to at least one or two per island with my weaker pets. I think it's because many of the grassland species are in the jungle plus your other species combined and there are like 6 different possible gaurdian monsters you can run into.

I dunno, I started with Jungles and barely got anything. When I switched to random was when I finally started collecting eggs. I'm using level 50 pets by the way. 

I just visited 20 islands with random leveled pets and only found 3 eggs.

I think the egg drop rate has been lowered? I only get 1 egg per ten faced guardians now. on Monday I got like three every ten guardian...

I think your right Chelona

Hey, with some further experimenting I figured out its not the biotype that really affects how many eggs you get. I think you have to rotate what biotypes your on, that's why random is working so well for people.. after trying about five times on a island it's probably a good time to switch to a new one... or try random

This theory os the best one I got and it makes sense more than any other I've heard but I might be wrong pease let me know if you have good results from trying this.