First it is nearly impossible to tell the sex of fry. Some maturity is necessary to see the signs of gender indication, in species that have gender indication. For instance you know you have a boy and girl angelfish only when you see hatched fry. Other than that, angels can be very difficult to tell. In general the following can be used as markers in helping determine gender. However, as with the English language, for every rule, there are exceptions.

Unless you have future breeding plans, most people prefer to purchase female tarantulas (when possible) due to their long lifespan (when compared to males of the same species). See similar questions...

There is no difference in appearance, between males and females. About the only sure way to tell the sex of a squirrel is to turn it over and look. Index See similar questions...

Is my female GSD in heat? How can I tell? Some dogs heat cycles may be shorter than average while other dogs may have longer ones. See similar questions...

It happens every four to five days, mostly in the evening hours, for twelve hours at a time. You will quite often see the other female(s) in the cage trying to mount the female in season. If you look at her vaginal opening, it will be open, moist, and kind of purplish in color. If you touch her hind quarters, she will stretch out, putting her nose and rear end in the air, arch her back downwards, and vibrate her ears. See similar questions...

The first telltale sign will be your queen beginning to nest, or to search for a place to have her kittens. By a bit more than halfway through the pregnancy, I start preparing a few nesting boxes. There are commercially available nesting boxes, but I find it easiest to use a cardboard box. They are readily available, highly customizable, and easy to clean (to the recycle bin with it!). See similar questions...

Chickens: There are several "theories" but one I have found to be the most accurate....is using a nail, needle or ring, fastened to a 6-8 inch piece of sewing thread. Hold the string with the nail swinging freely above the chick. The string will swing in a circle if it is a female and back and forth if it is a male. You can try this over people's wrists. It is fun and makes for very interesting conversation. I do not know why it works but we have found it to be very accurate. See similar questions...

Livebearers are voracious eaters and sometimes their stomachs bulge after a full meal. Pregnant livebearers bulge in the stomach area, and it doesn't subside after feeding time -- it just keeps growing. Light colored livebearers develop an obvious darkening of the skin, called a "gravid spot," right at the anal area. The spot enlarges and grows darker as the pregnancy progresses. It's like a window to the little babies inside. See similar questions...

There's no practical way. Not unless you can do some bloodwork, or observe the bird during mating season. See similar questions...

It's difficult to tell the difference. Generally, female frogs are slightly larger and their skin color is a little lighter than males. See similar questions...

The easiest way to tell is that the male hamster has a kind of extra bulge around the tail. But you can also turn them onto their back to check. You can see the difference between a male and female at See similar questions...

Sulcata Station's response: It is very difficult to determine the sex of a sulcata that is less than 10 to 15 pounds, or less than 12 inches in shell length. In fact, most sulcata owners *don't* know what sex their tortoise is until they witness it laying eggs, or everting its penis, or attempting to mount other tortoises. See similar questions...

For the most part, this is very simple. When they are young, or not completely mature, it is more difficult. The majority of the time, females will be short finned. They will also have an ovipositor between their ventral & anal fins. This looks like a small, white bump. They develop this when they are mature enough to breed. Males will normally have long, flowing fins. They are the typical picture that comes to mind when someone mentions a betta. See similar questions...

Answer: If it is singing, it's a male. The next best way is to flip them over and look at their belly. If the belly is streamlined and comes to a point like a sharpened pencil, it's a female. If the belly is fat and cigar-like and the end kind of looks like the top of the Capitol building in Washington D.C., it's a male. See similar questions...

One can shave the tummy and look for a spay scar. However, when veterinarians use certain stitching techniques, there is no scar whatsoever. Hopefully, these veterinarians will tattoo the tummy to indicate that the spaying surgery has been performed, but otherwise, the only way of knowing is to proceed with the surgery. See similar questions...

I don't think that you can really tell which is the male and female. Although some people say that males have larger mouths (for carrying eggs) and have a sharp edge to the stomach area. Although people here say that the female saratoga is the one that carries the eggs. So except for experts I don't think anybody can just tell by looking at them. See similar questions...