In warm climates, the fur is coarser and scarcer than in northern wolves. In populations where the resources are scarcer, more aggressive behaviours are likely to evolve. Song birds in particular are becoming scarcer and habitat loss has affected larger mammalian species. They are especially diverse in the arid areas of Australia, where other fauna are scarcer. But as resources became scarcer, their growth rates slowed until reaching the carrying capacity. German scientists were forced more and more to compete for ever scarcer resources. Some of the coins with particular mint marks are therefore scarcer than others. While businesses were expanding, the money they needed to finance that growth was becoming scarcer. Rations grow even scarcer and the men become anxious to return home. Insects are attracted to lights making them scarcer within the amphibian habitats. This scavenging behaviour is most common during the dry season when prey becomes scarcer. When food sources become scarcer, however, they separate once again. The electricity is turned off, and food is becoming scarcer and scarcer. As their supplies grow scarcer, Jenai and Riley are forced to ration. Since the middle 20th century, reforms there have gradually made flophouses scarcer.