Marbled Newt Breeding Question

[Buddy1996]

I was wondering if anyone can help me with a question about breeding issues with marbled newts. About a month ago, I received 4 marbled newts that were between 3 and 4 inches long. They all had red stripes down their backs, and the seller indicated that they all became efts in 2021 (but that two of the four had been from an earlier batch of offspring). I had requested 2 males and 2 females. I have reason to believe that they were in an outbuilding or outdoor enclosure because the seller said that the exact shipping date would depend on the weather. He is located in central Ohio. A couple of days after placing the newts into their new home (a 36-gallon tank consisting of a 50/50 mix of terrestrial area and aquatic area), three of the four newts entered the water and two of these lost their red stripe and grew very large tail fins and a short back crest. These two are about 3.75 inches long. The third aquatic newt is larger (about 4 inches) and still has the red stripe, but the tail fin is slightly webbed now. The fourth newt (measuring about 4.1 inches long) seems to have no interest in entering the water and is not eating as regular as the others either. My tank temperature ranges from about 65 degrees overnight to about 70 degrees during the day. Humidity is between 60 and 80 percent. I have live plants both on land and water, so I turn the lighting on from early morning until late evening. I’m wondering whether the newts in the water are old enough to breed. If they are as young as I was told, they shouldn’t be breeding yet, but doesn’t the development of the crest on the males indicate that they are entering into a breeding cycle? I am new to this, but I’ve read a lot on the topic. Still, I’m confused. Any help with understanding would greatly be appreciated.

 

[Herpin Man]

A 2021 marbled newt shouldn't be large enough to breed yet- unless it was REALLY heavily fed, which is doubtful. In fact, newts that young aren't likely big enough to be sexed reliable. Are you sure about that age?
When ready to breed, the males develop a very noticeable crest on their back, and the tail develops sort of a fin as well. So it sounds like you do have a couple of males.
If you were to post photos and sizes of the newts in question, it might provide a clearer picture of what is happening here.

 

[Buddy1996]

When I first received the newts, all four were virtually indistinguishable from one another. Now, two of the newts have fin-like tails. Their tails are currently about 1/8 of an inch tall and growing. The dorsal ridge is more pronounced when the newts are underwater than what you see in this image. They have grown considerably in length since I received them a month ago. The ones that look like males are 3.75 inches long, and the ones that look like females still have their red stripes and are 4 to 4.1 inches long.

 

[Herpin Man]

That’s definitely a male. You may get some breeding activity this season.

 

[Buddy1996]

That's good to know. I will be keeping an eye out for that in the future. Thank you!