and tradition with "hay bucking" competitions still held for fun at many rodeos and county fairs. Small square bales are often stacked mechanically or by hand in a crisscrossed fashion sometimes called a "haystack", "rick" or "hayrick". Rain tends to wash nutrition out of hay and can cause spoilage or mold; hay in small square bales is particularly susceptible to this. Small bales are therefore often stored in a haymow or hayshed. Haystacks built outside are often protected by tarpaulins. If this is not done, the top two layers of the stack are often lost to rot and mold, and if the stack is not arranged in a proper haystack, moisture can seep even deeper into the stack. The rounded shape and tighter compaction of round bales make them less susceptible to spoilage, as the water is less likely to penetrate into the bale. The addition of net wrap, which is not used on square bales, offers even greater weather resistance. People who keep small numbers of animals may prefer small bales that can be handled by one person without machinery. There is also a risk that hay bales may be moldy, or contain decaying carcasses of small creatures that were accidentally killed by baling equipment and swept up into the bale, which can produce toxins such as botulinum toxin. Both can be deadly to non-ruminant herbivores, such as horses, and when this occurs, the entire contaminated bale generally is thrown out, another reason some people continue to support the market for small bales. Large Bales Farmers who need to make large amounts of hay are likely to choose balers that produce much larger bales, maximizing the amount of hay that is protected from the elements. Large bales come in two types, round and square. Large square bales, which can weigh up to , can be stacked and are easier to transport on trucks. Large round bales, which typically weigh , are more moisture-resistant, and pack the hay more densely (especially at the center). Round bales are quickly fed with the use of mechanized equipment. The ratio of volume to surface area makes it possible for many dry-area farmers to leave large bales outside until they are consumed. Wet-area farmers and those in climates with heavy snowfall can stack round bales under a shed or tarp, but can also use a light but durable plastic wrap that partially encloses bales