Why is my new baby crested gecko hiding and not moving much?

She may be a bit cautious and apprehensive in her new environment. Give her a few days to acclimate. Confirm proper environmental parameters, especially heat /temperature. Low temps can affect activity in reptiles. make sure the lighting is not too bright also.

Those temperatures are much too cold for a crested gecko. Ideally, daytime temps should range between 78F and 85F with nighttime Temps no lower than the low 70s F. Low temps can affect appetite and activity in reptiles. Some form of prey is necessary as a protein source in addition to the fruit and vegetable mixes. Refer to the care sheet at the link below. http://www.reptilesmagazine.com/Care-Sheets/Lizards/Crested-Gecko/

If he isn't struggling or trying to escape, he's probably okay with being held. Don't hold him for too long initially. Gradually increase the handling time to acclimate him. Even though he doesn't struggle, it may still be stressful, so he'll return to a safe place when returned to the enclosure. As he adjusts to his new surroundings, he may begin to explore. A "best guess" on age would be 12 to 16 weeks. Reptiles have different growth rates depending on diet, availability of food and environmental factors.

Warm him up. Check your tank temps (ambient and basking). Low temps will affect activity and appetite. Use a timer to set a 12 hour light cycle. An infrared heat bulb can be used at night if room temp goes below 70F. See an experienced herp vet for an exam to diagnose illness or injury if symptoms persist. Follow the link for a comprehensive care sheet. http://geckoforums.net/f115-leopard-gecko-caresheets/54138.htm

Bump the temperature up to between 26 and 28 C. It's a small change, but 25C may be a bit to cool for Gargoyle geckos. Low temps can affect appetite and activity. The heat mat should be on one half of the tank. Lights can be turned off at night, but the heat source should stay on if nighttime temps drop. Makes sure the diet contains adequate amounts of vitamin D3. Without it, he is at risk of developing metabolic bone disease (MBD). A recommended diet is Repashy Crested Gecko diet. It is a powdered diet that can be reconstituted as needed. It can be found online or in most pet stores. The locusts fed should be gut loaded 24 hours prior to feeding. If he has a healthy appetite, submit a stool sample to your veterinarian or a vet experienced in treating reptiles to diagnose intestinal parasites. An exam with an​ experienced herp veterinarian would be strongly recommended to diagnose metabolic bone disease and to begin treatment. Supportive care may be indicated in light of the recent rapid weight loss.

A heat lamp isn't necessary unless the room where the cage is located is cold. Cresties do just fine at room temperature. A UVB light source isn't necessary either as long as you feed a diet containing adequate levels of Vitamon D3. That said, either won't harm him and it is a matter of personal preference. Be sure to monitor cage temps to make sure they don't go too high. There was no image attached to this question. Age can be difficult to determine if you don't have a hatch date. The reason being that growth can be dramatically affected by diet and environment. Contact the PetSmart where he was purchased. They should have records from the source/breeder which should include a hatch date or age.

Leopard geckos are nocturnal. He may be more active at night, while you are asleep. They spend most of the day in a secure place, such as the hide you have provided. He should have a hide on each end of the enclosure. Monitor the cage temp, as low temps can affect activity in reptiles.