Marine Mammals are reliable bioindicators of aquatic ecosystems health. Since cetacean highly relay on the use of sound for conspecifics interaction, feeding, and navigation, research in bioacoustics becomes fundamental to unravel the influence of anthropogenic activities on their environment and vocal behaviour. Unfortunately, the widespread of studies in this area are often limited for the lack of affordable equipment. This paper first describes how to build a low cost hydrophone suitable for cetacean acoustic research and then shows how to perform hydrostatic pressure tests and acoustic calibrations using easily available tools. Finally, field recordings of individuals of two dolphin species: long-beaked common dolphin (Delphinus capensis) and bottlenose dolphin (Tursiops truncatus) in La Paz Bay, Baja California Sur, Mexico using the proposed hydrophone and a professional hydrophone system [AQ-1s and ITC-1042 transducers (10 Hz -100 kHz)] are compared.

In ecology, bats have become a major subject of study. Some pollinate and disperse the seeds of many tropical plants; some help to control insect populations; a few affect livestock by sucking blood, but in all cases bats are indispensable links in ecosystems. Bats use of sound waves make echolocation calls monitoring a powerful tool for distribution, census, and present studies. This technique depends on having a reliable database of sounds for species identification purposes. Although there are several databases of echolocation sounds; the signal emitted by a bat depends on environmental conditions (vegetation, weather conditions), biotic factors (prey size, movement, defensive measures), and the specific task (seek, flee, pursue, evade, wandering, obstacle avoiding). This variability makes comparisons among databases difficult. A portable chamber made of common materials for in situ recording under controlled conditions is presented. The use of the chamber is proposed as a tool which might help to generate databases that could be reliable compared. Nine species of desert bats from the northwest region of Mexico were recorder using the chamber under controlled conditions and compared with field recordings. The performance of the chamber and the utility of the database generated for filed identification are presented.