This text is written to provide a mathematically sound but accessible and engaging introduction to Bayesian inference specifically for environmental scientists, ecologists and wildlife biologists. It emphasizes the power and usefulness of Bayesian methods in an ecological context. The advent of fast personal computers and easily available software has simplified the use of Bayesian and hierarchical models. One obstacle remains for ecologists and wildlife biologists, namely the near absence of Bayesian texts written specifically for them. The book includes many relevant examples, is supported by software and examples on a companion website and will become an essential grounding in this approach for students and research ecologists. It features: engagingly written text specifically designed to demystify a complex subject; examples drawn from ecology and wildlife research; an essential grounding for graduate and research ecologists in the increasingly prevalent; Bayesian approach to inference; a companion website with analytical software and examples; and, leading authors with world-class reputations in ecology and biostatistics.