Seven Black Caiman (Melanosuchus niger) nests were located and monitored at Limoncocha and Añangu lagoons (northeastern Ecuador), between October 2002 and March 2003. Melanosuchus niger nesting coincided with the annual low water level season in the Ecuadorian Amazon. Mean number of eggs per nest was 28 and 34 eggs at Limoncocha and Añangu, respectively. Egg chamber temperature was monitored in two nests during the incubation period and showed no relationship with external air temperature, suggesting that the nests have their own heating sources. Mean hatching success was 42.4%, and flooding of the nests was identified as the main cause of egg mortality (29% of all the eggs).

The trophic position of a top predator, synonymous with food-chain length, is one of the most fundamental attributes of ecosystems. Stable isotope ratios of nitrogen (δ¹⁵N) have been used to estimate trophic position of organisms due to the predictable enrichment of¹⁵N in consumer tissues relative to their diet. Previous studies in crocodilians have found upward ontogenetic shifts in their ‘trophic position’. However, such increases are not expected from what is known about crocodilian diets because ontogenetic shifts in diet relate to taxonomic categories of prey rather than shifts to prey from higher trophic levels. When we analysed dietary information from the literature on the four Amazonian crocodilians, ontogenetic shifts in dietary-based trophic position (TP_diet) were minimal, and differed from those estimated usingδ¹⁵N data (TP_SIA). Thus, ontogenetic shifts in TP_SIAmay result not only from dietary assimilation but also from trophic discrimination factors (TDF orΔ¹⁵N) associated with body size. Using a unique TDF value to estimate trophic position of crocodilians of all sizes might obscure conclusions about ontogenetic shifts in trophic position. Our findings may change the way that researchers estimate trophic position of organisms that show orders of magnitude differences in size across their life span.

Ecuador is one of the smallest and most densely populated countries in South America. In spite of this, it is also one of the 17 megadiverse countries worldwide and home to the largest number of species per unit area. Most aquatic ecosystems in mainland Ecuador have historically faced strong environmental pressures because the country’s economy has been based on the exploitation and trade of raw materials and agricultural products at a very high environmental cost. In this review, we provide a broad overview of the diversity of freshwater ecosystems and fish in mainland Ecuador. We address broadly current and historical threats to these ecosystems, including pollution due to oil extraction, mining activities, agriculture and the disruption of hydrological connectivity caused by hydroelectric dams. Despite these problems, we show some examples of promising initiatives at the local and national levels to address this situation.