Department of Physics, Chemistry and Biology (IFM)

Results

Number of tadpoles, juvenile and adult frogs

There was high variation in the number of individuals and occupancy rates among the six different areas (Table 3). The results show that there are three core areas with high numbers of the E. mysteriosus, namely the A-, B-, and D-area. Tadpoles could only be detected in two of the six areas (A- and D-area). In the E-area not one single frog or tadpole was encountered during the six visits. In total, 1006 frogs and 86 tadpoles were found, counting all areas. There were eight bromeliads that only had tadpoles (none juvenile or adult during all 6 visits), seven of them in the tadpole-rich D-area. In the A-area 32 tadpoles were found in 11 different bromeliads, giving a mean of 2.9 tadpoles per bromeliad that were used for tadpole release. In  the D-area 54 tadpoles were found in 22 bromeliads, giving a mean of 2.5 tadpoles per bromeliad that were used for tadpole release. At each visit the number of encountered frogs in the bromeliads ranged from 0-5 and the number of found tadpoles ranged from 0-11 per bromeliad. 

In th e Bromeliad Species 1, significantly higher presence of frogs (presence ≥1 time and ≥3 times ) were found on bromeliads that were wider, less sun exposed, containing deeper water cavities (Fig. 6-8) and growing at lower altitudes (Table 4). For presence of frogs all 6 times, there was a significant impact of lower sun exposure. Bromeliads with presence of tadpoles were significantly wider and had deeper water cavities than bromeliads without tadpoles. Moreover, bromeliads growing at lower altitudes had a significantly higher occupancy of both adults and juveniles. However, significantly more adults were found on bromeliads that were wider and contained deeper water cavities, while these factors had no significant impact on juveniles. On the opposite, juveniles were found to be more present on bromeliads having lower sun exposure compared to the presence of adults. Additionally, for all recorded presences of frogs (except tadpole presence and presence all 6 times), significantly higher presence of frogs were found in bromeliads growing at lower altitudes with a mean of 1153 m (range 895-1332 m) compared to bromeliads growing on higher altitudes with a mean of 1271 m (range 969-1723 m). Density of bromeliads had no significant effect on any level of frog or tadpole presence. 

For all bromeliad quality variables a correlation analysis was done (Table 5). For both bromeliad species’ the water depth was positively correlated to the width, wider bromeliads containing deeper water cavities. The sun exposure and the bromeliads’ altitude were as well positively correlated in both species, bromeliads at higher altitudes receiving higher sun exposure. Additionally for Bromeliad Species 1, correlations were found between sun exposure and water depth, sun exposure and density and m.a.s.l. and density. 

Dispersal, feeding and breeding behaviour

General notes were taken on the basic behaviours of the E. mysteriosus . Individual dispersal by the frogs were studied in detail while the activity, breeding and feeding behaviours were briefly observed.

For the dispersal, 187 encounters of adults and juveniles were photographed in the A-area. Of those 46 were recaptures by 25 frogs, which ranged from 2-6 recaptures per individual (mean was 2 recaptures). From the recaptures it was found that the frogs disperse in mean 20.5 m (range 0-113 m) between different bromeliads. 25 frogs were found at least once in the same bromeliad (0 m), 7 frogs were dispersing at least 2.5 m, 6 frogs were dispersing at least 5 m, 5 frogs were dispersing at least 7.5 m, 4 frogs at least 10 m and 2 frogs at least 17.5 m and a single frog at least 113 m (Fig. 9).

During direct observations on activity, the adults and juveniles when observed undisturbed, tended to walk more than jump when moving in more difficult terrain (as rock walls and trees), but could move fast and for longer distances by doing great jumps when disturbed or when moving on the forest floor. The frogs also seemed to dedicate large time on “moving” (see Ethogram, Table 2) inside and outside the bromeliads, mostly in shadowed spots. 

In regard to breeding behaviour, interesting tadpole release behaviours were observed. When an adult was found carrying tadpoles it was observed to move between the bromeliad leaves, backing down and making a quick dip into the water, sitting still on the leave, perhaps move a little bit, then go on to the next leaf to follow the same behaviour pattern there. When observing frogs without tadpoles they went head first into water cavities but all adults carrying tadpoles went back first. One adult also engaged in feeding while moving around between the leaves. When the adult decided to release a tadpole it entered a water cavity and became floating on the water surface, freely or with front legs as anchor on bromeliad leaf. While floating, the adult was gently caressing one of the tadpoles on its back with its hind legs (mean number of times 28 (range 25-32)) until it was released into the water. Only one tadpole was released in one water cavity. In the A-area the three adults were carrying 2, 3, 3 tadpoles respectively and those with three tadpoles did only release one tadpole the first evening, carrying on the tadpoles the next day. The one with two tadpoles released the tadpoles in one cavity each during the same evening. In the D-area, adults carrying tadpoles showed the same behaviour pattern as above. However, the carrying of tadpoles were higher than in A-area, observing adults carrying 4, 4 and 5 tadpoles respectively. One that had four tadpoles and the one that had five tadpoles were carrying one tadpole on the hind leg and the rest on their backs.

Adult and juvenile frogs were observed to be feeding on ants and small, winged flies both inside the bromeliad and outside on rock walls, forest floor and on other plants.