## 4 Discussion
### Horizontal Movements, Habitat Use, Revisitations, and Home Ranges
Our findings suggest that these ARS behaviors and revisitations are likely associated with both cleaning and foraging behaviors, as reef manta rays regularly spend multiple hours at certain aggregation sites and may stay close to the area for a few days or even weeks as they regularly alternate between cleaning and foraging [47], leading to measures of high residency and site affinity [11; 12]. The localized movements and high site affinity demonstrated by the satellite-tracked reef manta rays in all the tagging regions in Indonesia are likely at least partially explained by the high primary productivity in these areas. [PERSON] et al. [21] suggested that island formation comprising atolls or small island groups that are surrounded by or in the vicinity of deep waters often generates zooplankton accumulation, and therefore offers abundant food resources and leads to the strong residency of reef manta rays in these regions. Furthermore, the high residency is likely also influenced by the presence of cleaning stations, which are crucial for manta health and survival. Reef manta rays visit cleaning stations for a number of purposes, such as for parasite removal and social interactions [27; 48; 49]. In our study regions, many actively used feeding sites and cleaning stations have been identified in Sangalaki, Berau [25], Komodo [7], Nusa Penida [8], and Raja Ampat [50; 6]. Despite the species' ability to migrate seasonally between highly productive areas located several hundreds of kilometers away [51; 52; 16], our satellite-tagged reef manta rays only occasionally made long-distance movements within the study regions. Moreover, no movements of satellite-tracked individuals from one region to another were recorded. This is likely caused by several factors, including natural barriers (e.g., deep water such as that in the Makassar Strait and Banda Sea) and abundant prey availability reducing the need to migrate. Some studies suggest that deep waters, which imply a high risk of exposure to large predators when crossing them, are the primary barrier to the movements and long-distance migration of this species [53; 54; 55]. For example, deep water (up to 2000 m depth) may be responsible for the limited connectivity between the populations of reef manta rays located 150 km apart in Hawaii [56] and between two cleaning station sites in the northeast of New Caledonia [57]. Deep waters surround Berau and Raja Ampat (Makassar Strait and the Banda Sea, respectively) (Figure 4), separating these regions from the island chain of the Lesser Sundas, where Nusa Penida and Komodo are located. Furthermore, no movements of reef manta rays were recorded between Raja Ampat and the three other study regions in central Indonesia based on a comparison of the well-developed photo-ID catalogs of each of these areas [6; 7; 8]. The Banda Sea in central Indonesia also likely serves as a natural barrier to the movements of reef manta rays between Raja Ampat, the Lesser Sundas, and Berau. Similarly, the deep waters of the Makassar Strait likely serve as a barrier for reef manta rays to migrate between Berau and the Lesser Sundas. However, several movements of photo-identified reef manta rays were recorded between Nusa Penida and Komodo [58]. The small island chain of the Lesser Sundas that are connected by shallow reef systems (<300 m) seems to have encouraged several reef manta rays to undertake long-distance movements between the aggregation sites in Nusa Penida and Komodo [58], which are situated approximately 400 km apart. This is similar to the situation with the Great Barrier Reef in eastern Australia, where several reef manta rays were recorded (using photographic ID methods) moving up to 1150 km along the long stretch of uninterrupted shallow reef area which stretches north to south (these movements constitute the world's furthest known movements ever recorded for reef manta rays) [59].